Fresh water production method

ABSTRACT

Provided is a fresh water production method applying a combined water-treatment technology employing a plurality of semi-permeable membrane units, the method enabling prevention of problems caused by growth of a biofilm and allowing effective use of an injected chemical agent and an injected neutralizing agent. The fresh-water production method produces fresh water by treatment of source water by a semi-permeable membrane treatment device, the concentrated water resulting from the treatment by the semi-permeable membrane treatment device is mixed with other source water, and the water mixture is treated by a second semi-permeable membrane treatment device. A first chemical agent is injected continuously or intermittently into the source water and a second chemical agent is injected continuously or intermittently into the source water.

CROSS REFERENCE TO RELATED APPLICATIONS

The application is the U.S. National Phase application of PCTInternational Application No. PCT/JP2010/058524, filed May 20, 2010, andclaims priority to Japanese Patent Application No. 2009-191819, filedAug. 21, 2009 and Japanese Patent Application No. 2009-262488, filedNov. 18, 2009, the disclosures of which are each incorporated herein byreference in their entireties for all purposes.

FIELD OF THE INVENTION

The present invention relates to a fresh water production method usingcomposite water treatment technologies, more specifically a fresh waterproduction method for producing fresh water by a desalination technologyusing water (A) undergoing treatment and water (B) undergoing treatmentdifferent in osmotic pressure as multiple types of raw water.

BACKGROUND OF THE INVENTION

In recent years, the technical development of separation membranes hasprogressed, and owing to such features as space saving, labor saving andhigher filtered water quality, the use of separation membranes isexpanding in various fields including water treatment. For example,precision filtration membranes and ultrafiltration membranes are appliedto the water purification processes for producing industrial water andtap water from river water, groundwater and sewage treatment water, andapplied to the pretreatment in the reverse osmosis membrane treatmentprocesses for seawater desalination and to membrane separation activatedsludge processes. Nanofiltration membranes and reverse osmosis membranesare applied to ion removal, seawater desalination and wastewaterreutilization processes.

In the recent situation where water shortage is acute and chronic,seawater desalination using nanofiltration membranes and reverse osmosismembranes is actively pursued. In the nanofiltration membrane/reverseosmosis membrane filtration method requiring a supply pressure higherthan the osmotic pressure, a pump called “a booster pump” must be usedfor pressurization when raw water is supplied to nanofiltrationmembranes/reverse osmosis membranes. That is, if the salt concentrationof raw water supplied to nanofiltration membranes/reverse osmosismembranes is higher, the osmotic pressure is higher, and therefore it isnecessary to produce a higher pressure using a booster pump, and theenergy for operating the booster pump is necessary.

In order to solve these problems, for example, membrane process systemsin which advanced sewage treatment and seawater desalination areintegrated are developed (non-patent documents 1 and 2). According tothese technologies, the treatment of sewage by a membrane bioreactor isfollowed by the production of fresh water using reverse osmosismembranes, and further the concentrated water produced as a byproduct atthe time of separation by the reverse osmosis membranes is joined withseawater. Therefore, the salt concentration of supplied seawaterdeclines, and the pressurization by the booster pump for enforcing thereverse osmosis membrane separation for seawater desalination can bereduced. Thus, more energy-saving systems can be established.

Meanwhile, in a fresh water production system using semipermeablemembranes, in general, the deposition of organic matter and turbidmatter, the scale of metallic ions, the formation of the biofilm bymicrobial growth and the like can cause blocking on the surfaces of thesemipermeable membranes and in the semipermeable membrane treatmentapparatus, to bring about such troubles as the decrease in the quantityof produced fresh water and the rise of pressure. In particular, theformation of the biofilm is mainly caused by the microbes and substrate(carbon sources and nutrient salts) derived from the raw water, and themicrobial growth occurs not only on the surfaces of the semipermeablemembranes and in the semipermeable membrane treatment apparatus but alsoin the upstream piping. Accordingly troubles occur often. If the biofilmformed in a piping intermittently peels, the blocking of the channelsuch as the piping and tank and the abovementioned troubles of thesemipermeable membrane treatment apparatus are promoted. In order toprevent such troubles, it is necessary to sterilize the semipermeablemembrane treatment apparatus and the piping. Further, in the case whereraw water with much organic matter such as sewage is treated bysemipermeable membranes, the organic matter is deposited on the membranesurfaces, and microbes are likely to grow on the basis of the depositedorganic matter. Therefore, it is necessary to wash the semipermeablemembrane treatment apparatus using a chemical, for removing the organicmatter.

In the case of a fresh water production system in which advanced sewagetreatment and seawater desalination are integrated as described innon-patent document 1 or 2, the water obtained by treating sewage by amembrane bioreactor is treated as raw water by reverse osmosismembranes, to obtain fresh water, and the water concentrated by thereverse osmosis membranes, which is usually disposed as waste, is mixedwith seawater, for further treatment by reverse osmosis membranes. Inthe concentrated water, the carbon sources and nutrient salts as thesubstrate of microbes are more concentrated than those of thebiologically treated water, and consequently provide an environmentwhere microbes are likely to grow. Thus, there is a problem that since amicrobial film is formed in a concentrated water piping, the latterreverse osmosis membranes suffer troubles. Further, the aforementionedfresh water production system in which advanced sewage treatment andseawater desalination are integrated has an advantage that since thechemical used for the former reverse osmosis membranes is fed via theconcentrated water piping also into the latter reverse osmosismembranes, the chemical used in the former reverse osmosis membranes canbe reused also in the concentrated water piping and the latter reverseosmosis membranes. However, the chemical reused may decline in thewashing/sterilization effect as the case may be, and the former reverseosmosis membranes, the concentrated water piping and the latter osmosismembranes may require respectively different optimum chemicals as thecase may be. Therefore, the system has a problem that thewashing/sterilization effects in the concentrated water piping and thelatter reverse osmosis membranes are insufficient.

Further, it is known that a chemical such as sodium hypochlorite isadded immediately after water intake also on the seawater side, but thechemical is, for example, consumed for sterilization of piping ordiluted by joining/mixing with the concentrated water of the reverseosmosis membranes on the sewage side, to make the subsequentwashing/sterilization effect insufficient. Furthermore, a biofilm can beformed in the mixed water piping, to block the mixed water piping, thereverse osmosis membrane treatment apparatus or the safety filterthereof. Moreover, after seawater is joined/mixed with the concentratedwater of the reverse osmosis membranes on the sewage side, both thechemicals are mixed with each other or with a neutralizing agent, topose such a problem that the washing/sterilization effect is decreasedor that a harmful gas is generated. Further, in the case where achemical is injected into the water supplied to the latter reverseosmosis membrane treatment apparatus, there is such a problem that if achemical is newly injected though a chemical of the same type has beensupplied on the upstream side, the injected amount of the chemicals ofthe same type becomes excessive, or that the chemical or neutralizingagent supplied on the upstream side decreases the effect of the newlyinjected chemical.

Further, as described in patent document 1, known is a method in whichat least one chemical is added to the water supplied to reverse osmosismembranes and to the water concentrated by the reverse osmosismembranes, and the concentrated water is circulated into the watersupplied, for reusing the chemical. However, this method is notapplicable to a system for treating different types of raw water, andthere has been no conventional method for effectively using chemicals toallow reliable washing/sterilization of piping, tanks and the like in afresh water production system using a composite water treatmenttechnology.

LISTING OF DOCUMENTS Patent Document

-   Patent document 1: US Patent Application Publication No.    2006/0096920

Non-Patent Documents

-   Non-patent document 1: “Kobelco Eco-Solutions Co., Ltd., et al.,    “Model Project of Ministry of Economy, Trade and Industry:    Demonstration Experiment in Shunan City,” [online], Mar. 5, 2009,    Nihon Suido Shimbun, [retrieved on Jul. 2, 2009], internet    http://www.suido-gesuido.co.jp/blog/suido/2009/03/post_(—)2780.html-   Non-patent document 2: “Adoption of ‘Findings of Technical Series    Toward Low-Carbon Society—Social System Demonstration Model    Project,’” [online], Mar. 2, 2009, Toray Industries, Inc. Press    Release, [retrieved on Jul. 2, 2009], internet    http://www.toray.co.jp/news/water/nr090302.html

SUMMARY OF THE INVENTION

The invention provides a fresh water production method using a compositewater treatment technology with multiple semipermeable membrane unitsdisposed, as a fresh water production system capable of efficiently andeffectively using injected microbicides and neutralizing agents whilepreventing the troubles caused by biofilm formation.

The fresh water production method of this invention includes any of thefollowing exemplary configurations.

(1) A fresh water production method by treating water (A) undergoingtreatment by a semipermeable membrane treatment apparatus (A), toproduce fresh water, mixing the concentrated water (A) produced by thetreatment in the semipermeable membrane treatment apparatus (A) withwater (B) undergoing treatment, and treating the mixed water by asemipermeable membrane treatment apparatus (B), to produce fresh water,wherein a first chemical is continuously or intermittently injected intothe water (A) undergoing treatment and a second chemical is continuouslyor intermittently injected into the water (B) undergoing treatment.

(2) A fresh water production method, according to (1), wherein a thirdchemical is continuously or intermittently injected into theaforementioned concentrated water (A) and/or a fourth chemical iscontinuously or intermittently injected into the aforementioned mixedwater.

(3) A fresh water production method, according to (1) or (2), whereinthe concentration of the aforementioned first chemical in theaforementioned concentrated water (A) as discharged from theaforementioned semipermeable membrane treatment apparatus (A) is largerthan the concentration of the first chemical in the water (A) undergoingtreatment as supplied to the semipermeable membrane treatment apparatus(A).

(4) A fresh water production method, according to any one of (1) through(3), wherein a first neutralizing agent with an effect of deleting ordecreasing the washing effect and sterilization effect of the secondchemical is continuously or intermittently injected at a positionbetween a means for injecting the aforementioned second chemical and awater mixing means for mixing the aforementioned concentrated water (A)and the aforementioned water (B) undergoing treatment.

(5) A fresh water production method, according to (4), wherein theaforementioned first neutralizing agent has an effect of deleting ordecreasing the washing effect and sterilization effect of at least onechemical selected from the aforementioned first, third and fourthchemicals.

(6) A fresh water production method, according to (5), wherein theaforementioned first neutralizing agent is intermittently injected andthe first chemical is injected while the injection of the firstneutralizing agent is suspended, and/or the third chemical is injectedwhile the injection of the first neutralizing agent is suspended, and/orthe fourth chemical is injected while the injection of the firstneutralizing agent is suspended.

(7) A fresh water production method, according to any one of (2) through(6), wherein a second neutralizing agent with an effect of deleting ordecreasing the washing effect and sterilization effect of at least onechemical selected from the aforementioned first, second and thirdchemicals is injected continuously or intermittently at a positionbetween the water mixing means for mixing the aforementionedconcentrated water (A) and the aforementioned water (B) undergoingtreatment and a means for injecting the aforementioned fourth chemical.

(8) A fresh water production method, according to (7), wherein theaforementioned second neutralizing agent and the aforementioned fourthchemical are intermittently injected, and the fourth chemical isinjected while the injection of the second neutralizing agent issuspended.

(9) A fresh water production method, according to any one of (1) through(8), wherein in the case where the aforementioned first chemical is ofthe type identical to that of at least one chemical selected from theaforementioned second, third and fourth chemicals, the chemical of theidentical type is injected in such a manner that at least a portion ofthe chemical of the identical type can be mixed with the first chemical.

(10) A fresh water production method, according to any one of (2)through (8), wherein in the case where the aforementioned fourthchemical is of the type identical to that of at least one chemicalselected from the aforementioned first, second and third chemicals, thechemical of the identical type is injected in such a manner that atleast a portion of the chemical of the identical type can be mixed withthe fourth chemical.

(11) A fresh water production method, according to any one of (1)through (8), wherein in the case where the aforementioned first chemicalis of a type different from that of at least one chemical selected fromthe aforementioned second, third and fourth chemicals, the chemical ofthe different type is injected in such a manner that the chemical of thedifferent type cannot be mixed with the first chemical.

(12) A fresh water production method, according to any one of (2)through (8), wherein in the case where the aforementioned fourthchemical is of a type different from that at least one chemical selectedfrom the aforementioned first, second and third chemicals, the chemicalof the different type is injected in such a manner that the chemical ofthe different type cannot be mixed with the fourth chemical.

(13) A fresh water production method, according to (10), wherein a firstmeter selected from a pH meter, ORP meter, chlorine concentration meter,EC meter, TOC meter, ammonia meter, TN meter and DO meter is installedbetween the water mixing means for mixing the aforementionedconcentrated water (A) and the aforementioned water (B) undergoingtreatment and the aforementioned fourth chemical injection means,wherein the injection amount of the fourth chemical is decided on thebasis of the indicated value of the first meter.

(14) A fresh water production method, according to any one of (1)through (13), wherein in the case where at least one chemical selectedfrom the aforementioned first, second, third and fourth chemicals is anacid or alkali, the ORP value of the liquid is adjusted to be keptwithin a specified range of values at a position upstream of theinjection point of the chemical.

(15) A fresh water production method, according to (14), wherein in thecase where at least one chemical selected from the aforementioned first,second, third and fourth chemicals is an acid or alkali, a first ORPmeter for measuring the ORP value of the liquid, a fifth chemicalinjection means for continuously or intermittently injecting anoxidizing agent or reducing agent as a fifth chemical to the liquid, anda second ORP meter for measuring the ORP value of the liquid containingthe fifth chemical injected therein are installed in this order from theupstream side at positions upstream of all the injection means of theacid and alkali chemicals; the start of injecting the oxidizing agent orreducing agent by the fifth chemical injection means is decided inreference to the measured value of the aforementioned first ORP meter;and the stop of the injection is decided in reference to the measuredvalue of the aforementioned second ORP meter.

(16) A fresh water production method, according to any one of (1)through (15), wherein the ORP value of the concentrated water (A) ismeasured, and if the ORP value is larger than a specified value, theconcentrated water (A) is discharged outside the equipment, and thesemipermeable membrane treatment of the aforementioned semipermeablemembrane treatment apparatus (B) is stopped.

(17) A fresh water production method, according to any one of (1)through (16), wherein the aforementioned semipermeable membranetreatment apparatus (A) is provided with chlorine-resistantsemipermeable membranes, and the aforementioned first chemical is achlorine-based chemical.

(18) A fresh water production method, according to any one of (1)through (17), wherein the aforementioned semipermeable membranetreatment apparatus (B) is provided with chlorine-resistantsemipermeable membranes, and at least one chemical selected from theaforementioned second, third and fourth chemicals is a chlorine-basedchemical.

(19) A fresh water production method, according to any one of (1)through (17), wherein the aforementioned second chemical is achlorine-based chemical, and nitrogen-containing water is supplied asthe aforementioned water (A) undergoing treatment, and/or anitrogen-containing chemical is injected into the water (A) undergoingtreatment or the aforementioned concentrated water (A) or theaforementioned mixed water.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart showing an embodiment of the fresh waterproduction system to which this invention is applied.

FIG. 2 is a flowchart showing another embodiment of the fresh waterproduction system of this invention.

FIG. 3 is a flowchart showing a further other embodiment of the freshwater production system of this invention.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION

The effects obtained by this invention are as follows.

In one aspect of the invention, the first chemical injected into thewater (A) undergoing treatment washes/sterilizes the piping for feedingthe water (A) undergoing treatment to the semipermeable membranetreatment apparatus (A) and the semipermeable membrane treatmentapparatus (A) and is subsequently at least partially mixed with theconcentrated water (A), to wash/sterilize the piping for feeding theconcentrated water (A) to a water mixing means. Further, since theconcentrated water (A) containing the first chemical is mixed with thewater (B) undergoing treatment, the first chemical-containingconcentrated water (A) can at least partially provide the chemicalnecessary for washing/sterilizing the water mixing means for mixing theconcentrated water (A) and the water (B) undergoing treatment and thesemipermeable membrane treatment apparatus (B). Furthermore, the secondchemical injected into the water (B) undergoing treatmentwashes/sterilizes the piping for feeding the water (B) undergoingtreatment to the semipermeable membrane treatment apparatus (B), thewater mixing means and the semipermeable membrane treatment apparatus(B). Since chemicals are injected at least at two upstream positions asdescribed above, at least all the semipermeable membrane treatmentapparatuses and the pipings upstream thereof contacted by the respectivetypes of water undergoing treatment and the concentrated water likely togenerate microbes are disposed to contact the chemicals. Thus, theintended washing/sterilization effect can be obtained.

In another aspect of the invention, the piping of the concentrated water(A) of the semipermeable membrane treatment apparatus (A) can beeffectively washed/sterilized by continuously or intermittentlyinjecting the third chemical. Since the concentrated water (A) isobtained by concentrating the raw water of the semipermeable membranetreatment apparatus (A), the concentrated water (A) has a high microbialsubstrate concentration, and consequently a biofilm is likely to beformed in the piping. Further, it is possible to enhance thewashing/sterilization effect and to decrease the amounts of thechemicals used, by using different chemicals suitable for respectivesemipermeable membrane treatment apparatuses, pipings, etc. and makingup for the losses of the chemicals in the case where they are digestedby the semipermeable membrane treatment apparatuses.

Furthermore, the semipermeable membrane treatment apparatus (B) can beeffectively sterilized by continuously or intermittently injecting thefourth chemical into the mixed water. The first chemical and/or thesecond chemical and/or the third chemical are added on the upstreamside, but as the chemicals exhibit the washing/sterilization effects,the effects are gradually consumed. Therefore, as the case may be, thewashing/sterilization effect may become insufficient. Moreover, thewashing/sterilization effect can also be enhanced by using a chemicalfor a semipermeable membrane treatment apparatus different from that fora piping.

In another aspect of the invention, the washing/sterilization effect forthe piping of the concentrated water (A) can be expected since the firstchemical capable of maintaining the concentration of the first chemicalremaining in the concentrated water (A) of the semipermeable membranetreatment apparatus (A) is combined with the semipermeable membranetreatment apparatus (A). Further, in the case where the concentratedwater is diluted to X times after having been mixed with the water (B)undergoing treatment, the effect of washing/sterilizing the water mixingmeans and the mixed water piping can be expected if the first chemicalcapable of bringing the chemical concentration of the concentrated water(A) to X times the chemical concentration at the raw water inlet(primary side) of the semipermeable membrane treatment apparatus (A) iscombined with the semipermeable membrane treatment apparatus (A).

Another aspect of the invention is intended to allow avoiding the casewhere the second chemical lowers the function of the semipermeablemembrane treatment apparatus (B) and the case where the effects of thechemicals (the first chemical and/or the second chemical) supplied onthe side of the concentrated water (A) of the semipermeable membranetreatment apparatus (A) are deleted or decreased.

In the case where the aforementioned first neutralizing agent has aneffect of deleting or decreasing the washing/sterilization effects ofthe aforementioned first chemical and/or the aforementioned thirdchemical and/or the aforementioned fourth chemical and where the secondchemical lowers the function of the semipermeable membrane treatmentapparatus (B), the washing/sterilization effects of the first chemicaland/or the third chemical and/or the fourth chemical can be sustained bydeleting or decreasing the effect of the second chemical before theconcentrated water (A) of the semipermeable membrane treatment apparatus(A) and the water (B) undergoing treatment are mixed.

In another aspect of the invention, the chance for the firstneutralizing agent to contact the first chemical and/or the thirdchemical and/or the fourth chemical can be further decreased, and thewashing/sterilization effects of the first chemical and/or the thirdchemical and/or the fourth chemical can be sustained by injecting thefirst chemical and/or the third chemical and/or the fourth chemicalwhile the first neutralizing agent is not injected.

In another aspect of the invention, in the case where any chemical ofthe first, second and third chemicals decreases the function of thesemipermeable membrane treatment apparatus (B), it is preferred todelete or decrease the effect of the chemical before the chemical issupplied to the semipermeable membrane treatment apparatus (B).Therefore, the second neutralizing agent can be injected to decrease theeffect of the chemical before the chemical is supplied to thesemipermeable membrane treatment apparatus (B), so that the function ofthe semipermeable membrane treatment apparatus (B) can be maintained.However, this operation alone is insufficient for washing/sterilizingthe semipermeable membrane treatment apparatus (B). Consequently thesemipermeable membrane treatment apparatus (B) can be washed/sterilizedby injecting the fourth chemical after injecting the second neutralizingagent.

In this connection, in the case where the washing/sterilization effectof the fourth chemical is deleted or decreased by the secondneutralizing agent, if the fourth chemical is injected while theinjection of the second neutralizing agent is suspended as in oneembodiment of the invention, it can be prevented that the effect of thefourth chemical is deleted or decreased by the second neutralizing agentremaining in the mixed water, to enhance the washing/sterilizationeffect of the semipermeable membrane treatment apparatus (B).

In another aspect of the invention, if a chemical of the type identicalto that of the first chemical injected mainly for sterilizing thesemipermeable membrane treatment apparatus (A) is used as the secondchemical or the third chemical or the fourth chemical, the firstchemical remaining in the concentrated water (A) of the semipermeablemembrane treatment apparatus (A) can be effectively used. In general, achemical is considered to exhibit the washing/sterilization effectthereof at a certain concentration or higher. Therefore, if the secondchemical or the third chemical or the fourth chemical is additionallysupplied only to such an extent that the washing/sterilization effectcan be exhibited, the amount of the chemical injected can be reduced.Especially if the second chemical or the third chemical or the fourthchemical is injected when the first chemical is injected, the chemicalconcentration can be adjusted to the required minimum level at which thewashing/sterilization effect can be exhibited.

In another aspect of the invention, if a chemical of the type identicalto that of the first chemical or the second chemical or the thirdchemical injected on the side upstream of the injection point of thefourth chemical is used as the fourth chemical injected mainly forwashing/sterilizing the semipermeable membrane treatment apparatus (B),the chemical injected on the upstream side and remaining can beeffectively used. In general, a chemical is considered to exhibit thewashing/sterilization effect thereof at a certain concentration orhigher. Therefore, if the fourth chemical is additionally supplied onlyto such an extent that the washing/sterilization effect can beexhibited, the amount of the chemical injected can be reduced.

In one aspect of the invention, if a first meter selected from a pHmeter, ORP meter, chlorine concentration meter, EC meter, TOC meter,ammonia meter, TN meter and DO meter is installed between the watermixing means and the fourth chemical injection point, the indicatedvalue of the first meter is based on the concentration of the chemicalof the type identical to that of the fourth chemical, and on the basisof the indicated value of the first meter, the concentration of thechemical flowing into the fourth chemical injection point is estimatedto adjust the added amount of the fourth chemical, then the excess orshortage of the chemical concentration capable of exhibiting thewashing/sterilization effect can be minimized. Further, if the indicatedvalue of the first meter is based on the concentration of theneutralizing agent for neutralizing the fourth chemical and theconcentration of the neutralizing agent flowing into the fourth chemicalinjection point is estimated on the basis of the indicated value of thefirst meter, to adjust the added amount of the fourth chemical and thestart of fourth chemical injection, then the effect of the fourthchemical can be enhanced.

In the above, pH stands for potential hydrogen, which indicates thedegree of acidity or alkalinity of a substance. A smaller pH valueindicates stronger acidity, and on the contrary, a larger pH valueindicates stronger alkalinity. In general, since microbes grow in a pHrange from 6 to 8, the pH is often adjusted at lower than 6 or higherthan 8 for microbial sterilization. Further, for membrane washing, thepH is often adjusted at 2 to 4 in acid washing and 9 to 11 in alkaliwashing to remove organic matter and scale. In this invention, as the pHmeter for measuring the pH, any publicly known measuring instrument canbe used.

ORP stands for oxidation-reduction potential, which expresses thepotential generated when electrons are received and sent in anoxidation-reduction reaction. An oxidizing agent has a positive ORPvalue, since it takes electrons from another substance, and a reducingagent has a negative ORP value, since it gives electrons to anothersubstance. Further, a higher positive ORP value expresses a largeroxidizing power and a lower negative ORP value expresses a largerreducing power. In general, the ORP value of free chlorine is said to be750 mV or more and to be a strongly oxidizing agent. In this invention,as the ORP meter for measuring ORP, any publicly known measuringinstrument can be used.

A chlorine concentration refers to a free chlorine concentration or thetotal concentration of free chlorine and bound chlorine. Free chlorinehas a sterilization effect of destroying microbes at a large oxidizingpower. Further, bound chlorine like chloramines has an effectcorresponding to a fraction of the effect of free chlorine, but stillhas a relatively large sterilization effect. In this invention, as thechlorine concentration meter for measuring chlorine concentration, anypublicly known measuring instrument can be used.

EC stands for electronic conductivity, which expresses the total ionconcentration contained in water obtained by measuring the quantity ofelectricity flowing as a result of the migration of ions in the water. Ahigher EC means a higher ion concentration and EC can be used to measurethe amount of a chemical injected. In this invention, as an EC meter formeasuring EC, any publicly known measuring instrument can be used.

TOC stands for total organic carbon, which expresses the total amount ofthe organic matter capable of being oxidized in water, in terms of theamount of carbon. An organic acid such as citric acid is a chemicalcontaining carbon, and therefore the amount of the chemical can bemeasured by measuring TOC. In this invention, as a TOC meter formeasuring TOC, any publicly known measuring instrument can be used.

Ammonia is an alkali and if ammonia is combined with chlorine,chloramines are produced to provide a sterilization effect. In thisinvention, as an ammonia meter for measuring ammonia, any publicly knownmeasuring instrument can be used.

TN stands for total nitrogen, which expresses the total amount oforganic and inorganic (ammonia nitrogen, nitrite nitrogen and nitratenitrogen) nitrogen compounds. The amount of a chemical containingnitrogen such as a chloramine can be measured by measuring TN. In thisinvention, as the TN meter for measuring TN, any publicly knownmeasuring instrument can be used.

DO stands for dissolved oxygen. Microbes include aerobic microbes thatlike oxygen and anaerobic microbes that like a state free from oxygen.Aerobic microbes are inhibited if there is no DO in a liquid, andanaerobic microbes are inhibited if there is DO in a liquid.Consequently if a chemical capable of decreasing DO in a liquid, such assodium nitrite, is injected to control DO, the generation of microbescan be inhibited. In this invention, as the DO meter for measuring DO,any publicly known measuring instrument can be used.

In another aspect of the invention, the washing/sterilization effects ofthe piping downstream of the first chemical injection point and thesemipermeable membrane treatment apparatus (B) can be enhanced by usinga chemical of a type different from that of the first chemical injectedmainly for washing/sterilizing the semipermeable membrane treatmentapparatus (A), as the second chemical or the third chemical or thefourth chemical. In general, in the case where only one type ofchemicals is always used, microbes tolerant of the type of chemicals arelikely to be generated. Therefore, by using a chemical of a typedifferent from that of the first chemical as the second chemical or thethird chemical or the fourth chemical for washing/sterilizing the pipingor the semipermeable membrane treatment apparatus, the generation ofmicrobes tolerant of the type of chemicals can be inhibited to enhancethe washing/sterilization effect.

Especially by injecting the second chemical or the third chemical or thefourth chemical while the injection of the first chemical is suspended,the sterilization effect can be further enhanced. Further, in the casewhere the first chemical and the second chemical or the third chemicalor the fourth chemical are mixed with each other to exert a negativeinfluence, for example, to decrease the sterilization effect of eitherof them or to generate a harmful substance, such a negative influencecan be avoided.

In another aspect of the invention, the sterilization effect of thesemipermeable membrane treatment apparatus (B) can be enhanced by usinga chemical of a type different from that of the first chemical or thesecond chemical or the third chemical injected on the side upstream ofthe fourth chemical injection point is used as the fourth chemicalinjected mainly for sterilizing the semipermeable membrane treatmentapparatus (B).

Usually semipermeable membranes are weak to strong oxidizing agents suchas sodium hypochlorite, chlorine dioxide and hydrogen peroxide, andtherefore it is often practiced to measure the ORP value on the upstreamside for injecting a reducing agent for control. On the other hand,acids and alkalis are injected in order to wash/sterilize pipings andsemipermeable membrane treatment apparatuses, but acids and alkalischange the ORP value. Consequently if the ORP value of the liquid ismeasured before injecting an acid or alkali, the ORP value by anoxidizing agent such as remaining chlorine can be accurately identified,and if an adequate amount of a reducing agent is injected in response tothe amount of chlorine or the like remaining in the liquid, theremaining chlorine can be reliably inactivated, to prevent thedeterioration of the semipermeable membranes by the remaining chlorine.

In another aspect of the invention, the component capable ofdeteriorating the semipermeable membranes such as remaining chlorinecontained in the water undergoing treatment or mixed water can beinactivated to prevent the deterioration of the semipermeable membranes,by starting the injection of the fifth chemical in the case where thevalue measured by the first ORP meter installed at a position upstreamof the fifth chemical injection point is larger than a specified valueand stopping the injection of the fifth chemical in the case where thevalue measured by the second ORP meter installed at a positiondownstream of the fifth chemical injection point falls within the rangeof specified values. Further, it can be prevented that a wasteful amountof a chemical is injected.

In another aspect of the invention, if concentrated water with an ORPvalue capable of deteriorating the semipermeable membrane treatmentapparatus (B) is produced as the concentrated water (A), thedeterioration of the semipermeable membrane treatment apparatus (B) canbe prevented by discharging the concentrated water (A) outside thesystem from a valve. As a result, the amount of water supplied to thesemipermeable membrane treatment apparatus (B) decreases and the osmoticpressure of the water supplied to the semipermeable membrane treatmentapparatus (B) changes. Consequently, if the operation of thesemipermeable membrane treatment apparatus (B) is stopped, the damage ofthe semipermeable membrane treatment apparatus (B) can be prevented.

In another aspect of the invention, chlorine-resistant semipermeablemembranes are used in the semipermeable membrane treatment apparatus (A)so that a chlorine-based chemical such as sodium hypochlorite usuallyused for sterilization of pipings can be used as the first chemical, andstill after it is used for washing/sterilizing the semipermeablemembrane treatment apparatus (A), it can be used as it is forwashing/sterilizing the piping of the concentrated water (A) of thesemipermeable membrane treatment apparatus (A) and the semipermeablemembrane treatment apparatus (B).

In another aspect of the invention, chlorine-resistant semipermeablemembranes are used in the semipermeable membrane treatment apparatus (B)so that a chlorine-based chemical such as sodium hypochlorite usuallyused for sterilization of pipings can be used as the second chemical orthe third chemical or the fourth chemical, and that the chlorine-basedchemical used for washing the piping can be used as it is forwashing/sterilizing the semipermeable membrane treatment apparatus (B).

In another aspect of the invention, the chlorine-containing liquid asthe second chemical is mixed with a nitrogen component contained in thewater (A) undergoing treatment or an injected nitrogen-containingchemical, to generate chloramines, the sterilization effect of thechloramines can be used to wash the semipermeable membrane treatmentapparatus (B). In the case where the semipermeable membrane treatmentapparatus (B) does not have resistance against a strong oxidizing agentsuch as free chlorine, the washing by chloramines is effective. In thecase where the water (A) undergoing treatment is sewage or livestockwastewater or the like and contains a nitrogen component, the nitrogencomponent concentrated in the concentrated water (A) and thechlorine-containing liquid injected as the second chemical react witheach other to form chloramines. If the piping for feeding the water (B)undergoing treatment or the like is washed/sterilized by free chlorinewith strong washing/sterilization power, the free chlorine can be madeto react with the nitrogen component inflowing from the water (A)undergoing treatment, to produce chloramines for washing/sterilizing thesemipermeable membrane treatment apparatus (B). In this case, it is notnecessary to neutralize the free chlorine for preventing thedeterioration of the semipermeable membrane treatment apparatus (B).

Desirable modes for carrying out this invention are explained below inreference to drawings, though the scope of this invention is not limitedthereto or thereby.

FIG. 1 is a flowchart showing an embodiment of the fresh waterproduction system to which this invention is applied. This fresh waterproduction system is provided with a semipermeable membrane treatmentprocess (A)(100) for treating water (A)(1) undergoing treatment by asemipermeable membrane treatment apparatus (A)(2) and a semipermeablemembrane treatment process (B)(200) for treating water (B)(4) undergoingtreatment by a semipermeable membrane treatment apparatus (B)(6). Thesemipermeable membrane treatment process (A)(100) is provided with awater (A) undergoing treatment feed piping (101) for supplying the water(A)(1) to the semipermeable membrane treatment apparatus (A)(2), abooster pump (111) installed in the water (A) undergoing treatment feedpiping (101), for supplying the water (A)(1) undergoing treatment to thesemipermeable membrane treatment apparatus (A)(2), the semipermeablemembrane treatment apparatus (A) (2) communicating with the water (A)undergoing treatment feed piping (101), a membrane-permeating waterpiping (102) communicating with the secondary side (membrane-permeatingwater side) of the semipermeable membrane treatment apparatus (A), afirst chemical tank (10) for a first chemical used for washing thesemipermeable membrane treatment apparatus (A)(2) and/or the water (A)undergoing treatment feed piping (101), and a first chemical feed pump(11) as a first chemical injection means for continuously orintermittently injecting the first chemical into the water (A)undergoing treatment.

Further, the semipermeable membrane treatment process (B)(200) isprovided with a water (B) undergoing treatment feed piping (103) forsupplying the water (B)(4) undergoing treatment to a water mixing tank(5), a concentrated water (A) feed piping (104) communicating with theprimary side (water-undergoing-treatment side) of the semipermeablemembrane treatment apparatus (A)(2), for supplying the concentratedwater (A) to the water mixing tank (5) provided as a water mixing means,the water mixing tank (5) communicating with the water (B) undergoingtreatment feed piping (103) and the concentrated water (A) feed piping(104), for mixing the water (B)(4) undergoing treatment and theconcentrated water (A), to obtain mixed water, a mixed water feed piping(105) for supplying the mixed water to the semipermeable membranetreatment apparatus (B)(6), a booster pump (112) installed in the mixedwater feed piping (105), for supplying the mixed water to thesemipermeable membrane treatment apparatus (B)(6), the semipermeablemembrane treatment apparatus (B)(6) communicating the mixed water feedpiping (105), a membrane-permeating water piping (106) communicatingwith the secondary side (membrane-permeating water side) of thesemipermeable membrane treatment apparatus (B)(6), a concentrated waterpiping (107) communicating with the primary side(water-undergoing-treatment side) of the semipermeable membranetreatment apparatus, a second chemical tank (20) for a second chemicalused for washing the water (B) undergoing treatment feed piping (103),and a second chemical feed pump (21) as a second chemical injectionmeans for continuously or intermittently injecting the second chemicalinto the water (B) undergoing treatment.

In the above, it is preferred that a third chemical injection means forcontinuously or intermittently injecting a third chemical into theaforementioned concentrated water (A) and/or a fourth chemical injectionmeans for continuously or intermittently injecting a fourth chemicalinto the aforementioned mixed water are provided.

In the above, the water (A)(1) undergoing treatment refers to the feedwater supplied to the semipermeable membrane treatment apparatus (A)(2).Further, the water (A)(1) undergoing treatment is not especially limitedin properties or components, and can be, for example, sewage, industrialwastewater, seawater, brine water, lake water, river water, groundwater,etc. Further, the water obtained by subjecting these types water tobiological and/or physical and/or chemical pretreatment such asactivated sludge treatment, pre-filtration, precision filtrationmembrane treatment, ultrafiltration membrane treatment, activated carbontreatment, ozone treatment and ultraviolet irradiation treatment canalso be used as the water (A) undergoing treatment, for decreasing thefouling generated in the semipermeable membrane treatment apparatus(A)(2). The properties and components of the water (B)(4) undergoingtreatment are also the same as those of the water (A) undergoingtreatment. If the two types of raw water are combined in such a mannerthat the osmotic pressure of the aforementioned concentrated water (A)may be lower than the osmotic pressure of the aforementioned water (B)undergoing treatment, the osmotic pressure of the water (B) undergoingtreatment can be lowered by mixing with the concentrated water (A), andthe pressure rise level of the water supplied to the semipermeablemembrane treatment apparatus (B) can be kept low.

In order to keep the relationship of osmotic pressures as describedabove, it is only required to use raw water with a low osmotic pressureas the water (A) undergoing treatment and raw water with a high osmoticpressure as the water (B) undergoing treatment. It is preferred to usewater with a low salt concentration as the raw water with a low osmoticpressure and to use water with a high salt concentration as the rawwater with a high osmotic pressure. The water with a low saltconcentration can generally be sewage, industrial wastewater, riverwater or water obtained by pretreating the foregoing. Further the waterwith a high salt concentration can generally be seawater, salt lakewater or brine water. For example, a combination consisting of thesecondarily treated water obtained by treating sewage or wastewater by amembrane bioreactor as the water (A) undergoing treatment and seawateras the water (B) undergoing treatment can be employed.

Further, somewhere in the abovementioned various pipings, biochemicaland/or physical and/or chemical treatment such as activated sludgetreatment, pre-filtration, precision filtration membrane treatment,ultrafiltration membrane treatment, activated carbon treatment, ozonetreatment or ultraviolet irradiation treatment, or an intermediate tankor the like can also be provided.

Further, the semipermeable membrane treatment apparatuses (A) and (B)are not especially limited in form or materials, if they functionallyallow the permeating water to be separated from the concentrated waterby the semipermeable membranes installed in each apparatus. In thiscase, a semipermeable membrane refers to a membrane that does not allowsome components of the water undergoing treatment to permeate, and canbe, for example, a semipermeable membrane that allows a solvent topermeate and does not allow solutes to permeate. Examples of thesemipermeable membranes used in water treatment technology include nanofiltration membranes and reverse osmosis membranes. Nano filtrationmembranes or reverse osmosis membranes are required to have suchperformance that the solutes contained in the water undergoing treatmentcan be decreased to such a low concentration level as to allow theremaining water to be used as regenerated water. Specifically, it isrequested that the membranes have such performance that various ions ofsalts, mineral components, etc., for example, divalent ions such ascalcium ions, magnesium ions and sulfate ions, monovalent ions such assodium ions, potassium ions and chlorine ions, and dissolvable organicsubstances such as humic acid (molecular weight M_(w)≧100,000), fulvicacid (molecular weight M_(w)=100 to 1,000), alcohols, ethers andsaccharides can be blocked. An NF membrane is defined as a reverseosmosis filtration membrane having an operation pressure of 1.5 MPa orless, a fractional molecular weight of 200 to 1,000 and a sodiumchloride blocking rate of 90% or less, and a membrane that has afractional molecular weight smaller than said range and a blocking ratehigher than said range is called a reverse osmosis membrane (ROmembrane). Further, a reverse osmosis membrane close to a nanofiltration membrane is also called a loose reverse osmosis membrane.

Nano filtration membranes and reverse osmosis membranes are available ashollow fiber membranes and flat membranes in view of form, and both theforms can be applied in this invention. Further, to facilitate handling,a fluid separation element with hollow fiber membrane or flat membranesaccommodated in a housing can also be used. With regard to the fluidseparation element, in the case where flat nano filtration membranes orflat reverse osmosis membranes are used, for example, a cylindricalhousing accommodating a structure in which a membrane unit containingnano filtration membranes or reverse osmosis membranes, a permeatingwater channel material such as tricot and a water supply channelmaterial such as plastic are wound around a cylindrical central pipehaving numerous holes therethrough is preferred. A separation membranemodule in which multiple fluid separation elements, each as describedabove, are connected in series or in parallel to each other, is alsopreferred. In the fluid separation membrane, feed water is supplied fromone end into the unit, and the permeating water that permeates the nanofiltration membrane or reverse osmosis membrane before the feed waterreaches the other end flows into the central pipe, being taken out ofthe central pipe at the other end. On the other hand, the feed waterthat does not permeate the nano filtration membranes or reverse osmosismembranes is taken out as concentrated water at the other end.

As the material of the nano filtration membranes or reverse osmosismembranes, cellulose acetate or polymer material such as cellulose-basedpolymer, polyamide or vinyl polymer can be used. A typicalnanofiltration membrane/reverse osmosis membrane can be a celluloseacetate-based or polyamide-based asymmetric membrane or a compositemembrane having a polyamide-based or polyurea-based active layer.

Further, the respective pipings such as the water (A) undergoingtreatment feed piping (101), the membrane-permeating water piping (102),the water (B) undergoing treatment feed piping (103), the concentratedwater (A) feed piping (104), the mixed water feed piping (105), themembrane-permeating water piping (106) and the concentrated water piping(107) are not especially limited if they are of such a material and havesuch a form as functionally allowing liquid transfer. However, it ispreferred that the pipings are resistant against the properties of theliquid transferred, the properties of the chemicals injected and thepressures applied.

The booster pump (111) and the booster pump (112) respectively have apressure boosting function of pressurizing the water (A) undergoingtreatment and the mixed water, for feeding the liquids to thesemipermeable membrane treatment apparatuses for separation. In the casewhere the osmotic pressure of the liquid concerned is low, it ispreferred to install a supply pump for pressurizing the liquid concernedby supplying the liquid, and in the case where the osmotic pressure ofthe liquid concerned is high, it is preferred to install a pump forsupplying the liquid concerned and a booster pump for boosting thepressure of the liquid in order to perform membrane permeation and alsofor supplying it to the semipermeable membrane treatment apparatus.

The water mixing means is not especially limited in method or type, ifit can functionally mix the water (B) undergoing treatment and theconcentrated water (A). For example, a method using the aforementionedwater mixing tank (5), a method using a line mixer, a method using afeed pump or the like can be employed. For example, the water mixingtank (5) is not especially limited, if it can store mixed water and isnot deteriorated by the chemical concerned, neutralizing agent, etc.,and a concrete tank, fiber-reinforced plastic tank, plastic tank or thelike can be used. A stirring machine can also be installed for stirringin the tank.

Further, as the chemical injection means and the neutralizing agentinjection means described later, there are a method of installing a tankwith a stirrer halfway in a piping so that a chemical or neutralizingagent can be injected into said tank and mixed by a stirrer, a method ofinjecting a chemical or neutralizing agent into a piping at a positionupstream of a booster pump and mixing by the booster pump, a method ofinstalling a line mixer for mixing, etc. Furthermore, the chemical tanksand the neutralizing agent tanks are not especially limited, if they canstore the chemical or the neutralizing agent concerned and are made of amaterial incapable of being deteriorated by the chemical or neutralizingagent concerned. Fiber-reinforced plastic tanks, plastic tanks or thelike can be used. Further, the chemical injection means and theneutralizing agent injection means described later can be of continuousinjection type for continuously injecting the chemical or neutralizingagent concerned or of intermittent injection type for switching on/offusing a timer or signals, etc.

Further, the first chemical is injected to mainly wash/sterilize thewater (A) undergoing treatment feed piping (101) and/or thesemipermeable membrane treatment tank (A)(2). The second chemical isinjected to mainly wash/sterilize the water (B) undergoing treatmentfeed piping (103). The third chemical is injected to mainlywash/sterilize the concentrated water feed piping (104). The fourthchemical is injected to mainly wash/sterilize the semipermeable membranetreatment apparatus (B)(6). Specifically, acids such as oxalic acid,citric acid and sulfuric acid; reducing agents such as sodium bisulfite,sodium sulfite, sodium thiosulfate and oxalic acid; alkalis such assodium hydroxide and sodium ethylenediaminetetraacetate; oxidizingagents such as sodium hypophosphite, chlorine dioxide and hydrogenperoxide; microbicides such as 2,2-dibromo-3-nitropropionamide (DBNPA)and chloramines; and other chemicals such as surfactants and scalepreventives can be adequately selected for use.

However, since usually semipermeable membranes are weak to strongoxidizing agents such as sodium hypochlorite, chlorine dioxide andhydrogen peroxide, it is preferred to use microbicides other than strongoxidizing agents as the first and fourth chemicals used for mainlywashing/sterilizing the semipermeable membrane treatment apparatuses,excluding the case where the chlorine-resistant chemical described lateris applied. On the other hand, since these strong oxidizing agents arerelatively inexpensive and have strong microbicidal power, they aresuitable for sterilizing pipings, and can be used as the second andthird chemicals. However, in order not to lower the performance of thedownstream semipermeable membrane treatment apparatus (B), in the casewhere a strong oxidizing agent is used as the second chemical, it ispreferred to perfectly neutralize using the first neutralizing agentand/or second neutralizing agent described later, and in the case wherea strong oxidizing agent is used as the third chemical, it is preferredto perfectly neutralize using a reducing agent neutralizing agent suchas sodium bisulfite as the second neutralizing agent described later.

Meanwhile, as described before, the first chemical is used to mainlywash/sterilize the water (A) undergoing treatment feed piping (101)and/or the semipermeable membrane treatment apparatus (A)(2). However,the washing/sterilization of the water (A) undergoing treatment feedpiping (101) can be distinguished from the washing/sterilization of thesemipermeable membrane treatment apparatus (A)(2), by at first injectinga chemical suitable for the piping washing/sterilization and threateningto lower the performance of the semipermeable membrane treatmentapparatus (A)(2) such as sodium hypochlorite in order to wash/sterilizethe water (A) undergoing treatment feed piping (101), neutralizing by aneutralizing agent such as sodium bisulfite as a reducing agent, andfurther injecting a chemical (acid, microbicide, weak oxidizing agent,cyan-based microbicide, reducing agent, or the like) unlikely to lowerthe performance of the semipermeable membrane treatment apparatus (A).In this case, it is preferred that the chemical suitable for pipingwashing/sterilization and threatening to lower the performance of thesemipermeable membrane treatment apparatus (A)(2) is injected at aposition upstream of the water (A) undergoing treatment feed piping(101), and subsequently that the neutralizing agent and the chemicalunlikely to lower the performance of the semipermeable membranetreatment apparatus (A) are injected in this order along the downstreamdirection. Further, it is preferred that the neutralizing agent and thechemical unlikely to lower the performance of the semipermeable membranetreatment apparatus (A) are injected at positions immediately before thesemipermeable membrane treatment apparatus (A)(2), since the water (A)undergoing treatment feed piping (101) can be sterilized in a widerrange.

Further, it is preferred that the concentration of the aforementionedfirst chemical in the aforementioned condensed water (A) at the time ofdischarge from the semipermeable membrane treatment apparatus (A) islarger than the concentration of the first chemical in theaforementioned water (A) undergoing treatment at the time of supply tothe semipermeable membrane treatment apparatus (A). Furthermore, in thecase where the concentrated water of the semipermeable membranetreatment apparatus (A) is diluted to X times after having been mixedwith the water (B) undergoing treatment, it is preferred that the firstchemical capable of bringing the chemical concentration of theconcentrated water of the semipermeable membrane treatment apparatus (A)to X times the chemical concentration at the raw water inlet (primaryside) of the semipermeable membrane treatment apparatus (A) is combinedwith the semipermeable membrane treatment apparatus (A). As a specificmeans for achieving it, a method of using reverse osmosis membranes asthe semipermeable membranes and using a microbicide with a relativelylarge molecular weight such as 2,2-dibromo-3-nitrilopropioneamide(DBNPA) or a method of enhancing the separation performance by adjustingpH for ionization can be used.

Further, it is preferred that a first neutralizing agent injection meansfor continuously or intermittently injecting a first neutralizing agentwith an effect of deleting or decreasing the washing/sterilizationeffect of the aforementioned second chemical is installed between theaforementioned second chemical injection means and the aforementionedwater mixing means. If this mode is employed, it can be avoided that thesecond chemical lowers the function of the semipermeable membranetreatment apparatus (B) and that the effects of the chemicals (the firstchemical and/or the second chemical) supplied from the concentratedwater side of the semipermeable membrane treatment apparatus (A) aredeleted or decreased.

Further in the abovementioned mode, it is especially preferred that theaforementioned first neutralizing agent has an effect of deleting ordecreasing the washing/sterilization effect of at least one chemicalselected from the aforementioned first, third and fourth chemicals. Ifthis mode is employed, in the case where the aforementioned firstneutralizing agent has an effect of deleting or decreasing thewashing/sterilization effect of the first chemical and/or the thirdchemical and/or the fourth chemical and where the second chemical lowersthe function of the semipermeable membrane treatment apparatus (B), theeffect of the second chemical is deleted or decreased before theconcentrated water of the semipermeable membrane treatment apparatus (A)and the water (B) undergoing treatment are mixed, so that thewashing/sterilization effect of the first chemical and/or the thirdchemical and/or the fourth chemical can be sustained.

Further, it is preferred that the aforementioned first neutralizingagent injection means intermittently injects the first neutralizingagent, and in addition the aforementioned first chemical injection meansintermittently injects the first chemical, wherein while the injectionof the first neutralizing agent by the first neutralizing agentinjection means is suspended, the first chemical injection means injectsthe first chemical; and/or that that the aforementioned third chemicalinjection means intermittently injects the third chemical, wherein whilethe injection of the first neutralizing agent by the first neutralizingagent injection means is suspended, the third chemical injection meansinjects the third chemical; and/or that the aforementioned fourthinjection means intermittently injects the fourth chemical, whereinwhile the injection of the first neutralizing agent by the firstneutralizing agent injection means is suspended, the fourth chemicalinjection means injects the fourth chemical. If this mode is employed,the chance of allowing the first neutralizing agent to contact the firstchemical and/or the third chemical and/or the fourth chemical can befurther decreased, and the sterilization effects of the first chemicaland/or the third chemical and/or the fourth chemical can be sustained.

Further, it is preferred that the second meter (115) is installedbetween the aforementioned second chemical injection means and theaforementioned first neutralizing agent injection means, wherein theinjection amount of the second chemical by the second chemical injectionmeans is decided on the basis of the indicated value of the second meter(115).

In this description, the first neutralizing agent and the secondneutralizing agent described later are not especially limited, if theyhave an effect of deleting or decreasing the washing/sterilizationeffects of the chemicals concerned. Specific combinations betweenchemicals and corresponding neutralizing agents are compiled in Table 1.

TABLE 1 Type of microbicide Examples of microbicide Type of neutralizingagent Examples of neutralizing agent Acid microbicide Oxalic acid,citric acid, Alkali neutralizing agent Sodium hydroxide, sodium sulfuricacid ethylenediaminetetraacetate Alkali microbicide Sodium hydroxide,sodium Acid neutralizing agent Oxalic acid, citric acid, sulfuricethylenediaminetetraacetate acid Strong oxidizing Sodium hypochlorite,Reducing agent Sodium bisulfite, sodium sulfite, agent chlorine dioxide,hydrogen sodium thiosulfate, oxalic acid peroxide, ozone Weak oxidizingChloramines agent Cyan-based 2,2-dibromo-2- nitrilopropioneamide (DBNPA)Reducing agent Sodium bisulfite, sodium Oxidizing agent Sodiumhypochlorite, chlorine sulfite, sodium thiosulfate, dioxide, hydrogenperoxide, oxalic acid ozone, chloramines

Further, if the indicated value of the second meter is based on theconcentration of the chemical of the type identical to that of thesecond chemical, and the concentration of the chemical flowing into thefirst neutralizing agent injection point is estimated on the basis ofthe indicated value of the second meter, to adjust the injection amountof the first neutralizing agent, then the second chemical can beneutralized without excess or shortage. By this operation, the injectionamount of the neutralizing agent can be minimized to prevent theexcessive injection of the neutralizing agent and to prevent thenegative influences (decline of semipermeable membrane performance,deletion or decrease of effects of chemicals and neutralizing agent onthe downstream side, generation of harmful byproduct, etc.) on thedownstream side by the otherwise excessively injected neutralizingagent. Specifically, in the case where an acid or alkali is used as thesecond chemical, a pH meter can be used as the second meter. Further, inthe case where an oxidizing agent or reducing agent is used as thesecond chemical, an ORP meter can be used as the second meter. Further,in the case where chlorine-containing water is used as the secondchemical, a chlorine concentration meter can also be used as the secondmeter.

Further, methods for deciding the injection amount of the firstneutralizing agent by the first neutralizing agent injection means onthe basis of the indicated value of the second meter include a method inwhich the calculation formula for estimating the chemical concentrationfrom the indicated value of the second meter is decided in advance; thefirst neutralizing agent injection amount necessary for neutralizing thesecond chemical is calculated from the calculation formula; and the flowrate of the first neutralizing agent feed pump is changed in order toinject the first neutralizing agent by an amount responding to the firstneutralizing agent injection amount. As another method, multiple firstneutralizing agent feed pumps can be prepared in advance, and the pumpsto be turned on and off are decided and operated in response to theindicated value of the second meter.

Further, it is preferred that the aforementioned fourth chemicalinjection means is provided, and that a second neutralizing agentinjection means for continuously or intermittently injecting a secondneutralizing agent with an effect of deleting or decreasing thewashing/sterilization effect of at least one chemical selected from theaforementioned first, second and third chemicals is installed betweenthe aforementioned water mixing means and the fourth chemical injectionmeans. In the case where any chemical selected from the first, secondand third chemicals decreases the function of the semipermeable membranetreatment apparatus (B), if this mode is employed, the secondneutralizing agent is injected to decrease the effect of the chemicalconcerned before the chemical concerned is supplied to the semipermeablemembrane treatment apparatus (B), for allowing the function of thesemipermeable membrane treatment apparatus (B) to be sustained.

Further, it is preferred that the aforementioned second neutralizingagent injection means intermittently injects the second neutralizingagent, while the aforementioned fourth chemical injection meansintermittently injects the fourth chemical, wherein the fourth chemicalinjection means injects the fourth chemical while the injection of thesecond neutralizing agent by the second neutralizing agent injectionmeans is suspended. If this mode is employed, the deletion or decreaseof the fourth chemical by the second neutralizing agent remaining in themixed water can be reduced or inhibited to enhance thewashing/sterilization effect of the semipermeable membrane treatmentapparatus (B).

In the case where the safety filter (113) for preventing the inflow of aturbidity component into the semipermeable membrane treatment apparatus(B) is installed in the mixed water feed piping (105), it is preferredto install the safety filter (113) between the water mixing means (watermixing tank (5)) an the second neutralizing agent injection means.

It is preferred that the first chemical is of the type identical to thatof at least one chemical selected from the aforementioned second, thirdand fourth chemicals. If this mode is employed, the first chemicalremaining in the concentrated water of the semipermeable membranetreatment apparatus (A) can be effectively used. In general, it isconsidered that a chemical is considered to exhibit awashing/sterilization effect at a certain concentration or higher, andtherefore if the second or third or fourth chemical is additionallysupplied only to such an extent that the washing/sterilization effectcan be exhibited, the injection amount of the chemical can be decreased.

Further, it is preferred that the aforementioned second chemicalinjection means injects the second chemical while the aforementionedfirst chemical injection means injects the first chemical, and/or thatthe aforementioned third chemical injection means injects the thirdchemical while the aforementioned first chemical injection means injectsthe first chemical, and/or that the aforementioned fourth chemicalinjection means injects the fourth chemical while the aforementionedfirst chemical injection means injects the first chemical. If this modeis employed, the chemical concentrations can be adjusted to the requiredminimum at which the washing/sterilization effects are exhibited.

In the above, a chemical of an identical type means that a chemical ofan identical chemical species is contained. For example, if the firstchemical and the second chemical are acid-based chemicals, the firstchemical is regarded to be of the type identical to that of the secondchemical. The same applies also to alkali-based chemicals, strongoxidizing agent-based chemicals, weak oxidizing agent-based chemicals,cyan-based chemicals and reducing agent-based chemicals.

Further, it is preferred that the aforementioned fourth chemicalinjection means is provided, and that the fourth chemical injected bythe fourth chemical injection means is of the type identical to that ofat least one chemical selected from the aforementioned first, second andthird chemicals. If this mode is employed, the remaining chemicalinjected on the upstream side can be effectively used. In general, achemical is considered to exhibit a washing/sterilization effect at acertain concentration or higher, and therefore if the fourth chemical isadditionally supplied only to such an extent that thewashing/sterilization effect can be exhibited, the injection amount ofthe chemical can be decreased.

Further, it is preferred that the first meter (114) is installed betweenthe aforementioned water mixing means and the aforementioned fourthchemical injection means, and that the injection amount of the fourthchemical by the fourth chemical injection means is decided on the basisof the indicated value of the first meter (114).

In the above, if the indicated value of the first meter (114) is basedon the concentration of the chemical of the type identical to that ofthe fourth chemical, and the concentration of the chemical flowing intothe fourth chemical injection point is estimated on the basis of theindicated value of the first meter (114), to adjust the added amount ofthe fourth chemical, then the excess or shortage of the chemicalconcentration capable of exhibiting the washing/sterilization effect canbe minimized. Specifically when an acid or alkali is used as thechemical, a pH meter can be used as the first meter (114). Further, anoxidizing agent or reducing agent is used as the chemical, an ORP metercan be used as the first meter (114). Furthermore, ifchlorine-containing water is used as the chemical, a chlorineconcentration meter can also be used as the first meter (114).

Further, methods for deciding the injection amount of the fourthchemical by the fourth chemical injection means on the basis of theindicated value of the first meter (114) include a method in which acalculation formula for estimating the chemical concentration from theindicated value of the first meter (114) is decided in advance; thechemical injection amount necessary for exhibiting thewashing/sterilization effect is calculated from the calculation formula;and the flow rate of the fourth chemical feed pump is changed to injectthe chemical by an amount responding to the chemical injection amount.As another method, multiple fourth chemical feed pumps are prepared inadvance, and the pumps to be turned on and off are decided and operatedin response to the indicated value of the first meter (114).

Further, the indicated value of the first meter (114) is based on theconcentration of the neutralizing agent for neutralizing the fourthchemical, and the concentration of the neutralizing agent flowing intothe fourth chemical injection point can be estimated on the basis of theindicated value of the first meter (114), to adjust the added amount ofthe fourth chemical and the start of fourth chemical injection, forenhancing the effect of the fourth chemical. Specifically, in the casewhere the neutralizing agent is an acid or alkali, a pH meter can beused as the first meter (114). Further in the case where theneutralizing agent is an oxidizing agent or reducing agent, an ORP metercan be used as the first meter (114). Furthermore in the case wherechlorine-containing water is used as the neutralizing agent, a chlorineconcentration meter can also be used as the first meter (114).

Further, it is preferred that the first chemical is a chemical of a typedifferent from that of at least one chemical selected from theaforementioned second, third and fourth chemicals. If this mode isemployed, the washing/sterilization effects of the piping downstream ofthe first chemical injection point and the semipermeable membranetreatment apparatus (B) can be enhanced. In general, in the case whereonly one type of chemicals is always used, microbes tolerant of the typeof chemicals are likely to be generated. Therefore, by using a chemicalof a type different from that of the first chemical as the secondchemical or the third chemical or the fourth chemical forwashing/sterilizing a piping or semipermeable membrane treatmentapparatus, the generation of microbes tolerant of a particular type ofchemicals can be inhibited to enhance the washing/sterilization effect.

Further, it is preferred that the aforementioned second chemicalinjection means injects the second chemical while the aforementionedfirst chemical injection means does not inject the first chemical,and/or that the aforementioned third chemical injection means injectsthe third chemical while the aforementioned first chemical injectionmeans does not inject the first chemical, and/or that the fourthchemical injection means injects the fourth chemical while theaforementioned first injection means does not inject the first chemical.If this mode is employed, the washing/sterilization effect can befurther enhanced. Further, in the case where the first chemical and thesecond chemical or the third chemical or the fourth chemical are such acombination as to cause a negative influence such as decreasing thewashing/sterilization effect of either of the chemicals or generating aharmful substance, when both the chemicals are mixed, the negativeinfluence can be avoided.

In the above, a chemical of a different type means a chemical, the maincomponent of which is of a different chemical species, that is, not theaforementioned chemical of an identical type. For example, if the firstchemical is an acid while the second microbicide is a strong oxidizingagent, they are regarded to be of different types.

Further, it is preferred that the aforementioned fourth chemicalinjection means is provided and that the fourth chemical injected by thefourth chemical injection means is of a type different from that of atleast one chemical selected from the aforementioned first, second andthird chemicals. If this mode is employed, the washing/sterilizationeffect of the semipermeable membrane treatment apparatus (B) can beenhanced.

Further, it is preferred that the first meter (114) selected from a pHmeter, ORP meter, chlorine concentration meter, EC meter, TOC meter,ammonia meter, TN meter and DO meter is installed between theaforementioned water mixing means and the aforementioned fourth chemicalinjection means, wherein the injection amount of the fourth chemical bythe fourth chemical injection means is decided on the basis of theindicated value of the first meter (114).

In the above, if the indicated value of the first meter (114) is basedon the concentration of the first chemical or the second chemical or thethird chemical and it is confirmed on the basis of the indicated valueof the first meter (114) that the first chemical or the second chemicalor the third chemical is not contained or has a certain concentration orlower in the inflow water flowing into the fourth chemical injectionpoint, then the injection start or injection amount of the fourthchemical can be adjusted to further enhance the washing/sterilizationeffect. Specifically, if the chemical is an acid or alkali, a pH metercan be used as the first meter (114). Further, if the chemical is anoxidizing agent or reducing agent, an ORP meter can be used as the firstmeter (114). Furthermore, if chlorine-containing water is used as thechemical, a chlorine concentration meter can also be used as the firstmeter (114). Furthermore, in the case where the EC of the chemical ismeasured to decide the injection amount, an EC meter can be used as thefirst meter (114). Moreover, in the case where an organic acid such ascitric acid is used as the chemical, a TOC meter can be used as thefirst meter (114). Further, in the case where ammonia is used as thechemical, an ammonia meter can be used as the first meter (114).Furthermore, in the case where a nitrogen-containing chemical such asammonia or chloramines is used as the chemical, a TN meter can be usedas the first meter (114). Moreover, if a chemical capable of changingdissolved oxygen such as sodium nitrite is used as the chemical, a DOmeter can be used as the first meter (114).

Further, if the indicated value of the first meter (114) is based on theconcentration of the neutralizing agent for neutralizing the fourthchemical and the concentration of the neutralizing agent flowing intothe fourth chemical injection point is estimated on the basis of theindicated value of the first meter (114), to adjust the added amount orinjection start of the fourth chemical, then the effect of the fourthchemical can be enhanced. Specifically in the case where theneutralizing agent is an acid or alkali, a pH meter can be used as thefirst meter (114). Further, in the case where the neutralizing agent isan oxidizing agent or reducing agent, an ORP meter can be used as thefirst meter (114). Moreover, in the case where the neutralizing agent ischlorine-containing water, a chlorine concentration meter can also beused as the first meter (114).

Examples of the first chemical, second chemical, third chemical, fourthchemical, first neutralizing agent and second neutralizing agentsatisfying the abovementioned matters are listed in Tables 2-1 to 2-15.

TABLE 2-1 First Second Third Fourth First Second microbicide microbicidemicrobicide microbicide neutralizing agent neutralizing agent {circlearound (1)} Acid/alkali Strong oxidizing Strong oxidizing Acid/alkaliReducing agent Reducing agent agent agent {circle around (2)}Acid/alkali Strong oxidizing Strong oxidizing Weak oxidizing Reducingagent Reducing agent agent agent agent/cyan-based {circle around (3)}Acid/alkali Strong oxidizing Strong oxidizing Reducing agent Reducingagent Reducing agent agent agent {circle around (4)} Acid/alkali Strongoxidizing Strong oxidizing Nil Reducing agent Reducing agent agent agent{circle around (5)} Acid/alkali Strong oxidizing Strong oxidizingAcid/alkali Nil Reducing agent agent agent {circle around (6)}Acid/alkali Strong oxidizing Strong oxidizing Weak oxidizing NilReducing agent agent agent agent/cyan-based {circle around (7)}Acid/alkali Strong oxidizing Strong oxidizing Reducing agent NilReducing agent agent agent {circle around (8)} Acid/alkali Strongoxidizing Strong oxidizing Nil Nil Reducing agent agent agent {circlearound (9)} Acid/alkali Strong oxidizing Acid/alkali Acid/alkali Nil Nilagent {circle around (10)} Acid/alkali Strong oxidizing Acid/alkali Weakoxidizing Nil Nil agent agent/cyan-based {circle around (11)}Acid/alkali Strong oxidizing Acid/alkali Reducing agent Nil Nil agent{circle around (12)} Acid/alkali Strong oxidizing Acid/alkali Nil NilNil agent {circle around (13)} Acid/alkali Strong oxidizing Weakoxidizing Acid/alkali Nil Nil agent agent/cyan-based {circle around(14)} Acid/alkali Strong oxidizing Weak oxidizing Weak oxidizing Nil Nilagent agent/cyan-based agent/cyan-based {circle around (15)} Acid/alkaliStrong oxidizing Weak oxidizing Reducing agent Nil Nil agentagent/cyan-based {circle around (16)} Acid/alkali Strong oxidizing Weakoxidizing Nil Nil Nil agent agent/cyan-based {circle around (17)}Acid/alkali Strong oxidizing Reducing agent Acid/alkali Nil Nil agent{circle around (18)} Acid/alkali Strong oxidizing Reducing agent Weakoxidizing Nil Nil agent agent/cyan-based {circle around (19)}Acid/alkali Strong oxidizing Reducing agent Reducing agent Nil Nil agent{circle around (20)} Acid/alkali Strong oxidizing Reducing agent Nil NilNil agent

TABLE 2-2 First Second Third Fourth First Second microbicide microbicidemicrobicide microbicide neutralizing agent neutralizing agent {circlearound (1)} Acid/alkali Nil Strong oxidizing Acid/alkali Reducing agentNil agent {circle around (2)} Acid/alkali Nil Strong oxidizing Weakoxidizing Reducing agent Nil agent agent/cyan-based {circle around (3)}Acid/alkali Nil Strong oxidizing Reducing agent Reducing agent Nil agent{circle around (4)} Acid/alkali Nil Strong oxidizing Nil Reducing agentNil agent {circle around (5)} Acid/alkali Nil Strong oxidizingAcid/alkali Nil Reducing agent agent {circle around (6)} Acid/alkali NilStrong oxidizing Weak oxidizing Nil Reducing agent agentagent/cyan-based {circle around (7)} Acid/alkali Nil Strong oxidizingReducing agent Nil Reducing agent agent {circle around (8)} Acid/alkaliNil Strong oxidizing Nil Nil Reducing agent agent {circle around (9)}Acid/alkali Nil Acid/alkali Acid/alkali Nil Nil {circle around (10)}Acid/alkali Nil Acid/alkali Weak oxidizing Nil Nil agent/cyan-based{circle around (11)} Acid/alkali Nil Acid/alkali Reducing agent Nil Nil{circle around (12)} Acid/alkali Nil Acid/alkali Nil Nil Nil {circlearound (13)} Acid/alkali Nil Weak oxidizing Acid/alkali Nil Nilagent/cyan-based {circle around (14)} Acid/alkali Nil Weak oxidizingWeak oxidizing Nil Nil agent/cyan-based agent/cyan-based {circle around(15)} Acid/alkali Nil Weak oxidizing Reducing agent Nil Nilagent/cyan-based {circle around (16)} Acid/alkali Nil Weak oxidizing NilNil Nil agent/cyan-based {circle around (17)} Acid/alkali Nil Reducingagent Acid/alkali Nil Nil {circle around (18)} Acid/alkali Nil Reducingagent Weak oxidizing Nil Nil agent/cyan-based {circle around (19)}Acid/alkali Nil Reducing agent Reducing agent Nil Nil {circle around(20)} Acid/alkali Nil Reducing agent Nil Nil Nil

TABLE 2-3 First Second Third Fourth First Second microbicide microbicidemicrobicide microbicide neutralizing agent neutralizing agent {circlearound (1)} Acid/alkali Acid/alkali Strong oxidizing Acid/alkaliReducing agent Reducing agent agent {circle around (2)} Acid/alkaliAcid/alkali Strong oxidizing Weak oxidizing Reducing agent Reducingagent agent agent/cyan-based {circle around (3)} Acid/alkali Acid/alkaliStrong oxidizing Reducing agent Reducing agent Reducing agent agent{circle around (4)} Acid/alkali Acid/alkali Strong oxidizing NilReducing agent Reducing agent agent {circle around (5)} Acid/alkaliAcid/alkali Strong oxidizing Acid/alkali Nil Nil agent {circle around(6)} Acid/alkali Acid/alkali Strong oxidizing Weak oxidizing Nil Nilagent agent/cyan-based {circle around (7)} Acid/alkali Acid/alkaliStrong oxidizing Reducing agent Nil Nil agent {circle around (8)}Acid/alkali Acid/alkali Strong oxidizing Nil Nil Nil agent {circlearound (9)} Acid/alkali Acid/alkali Acid/alkali Acid/alkali Nil Nil{circle around (10)} Acid/alkali Acid/alkali Acid/alkali Weak oxidizingNil Nil agent/cyan-based {circle around (11)} Acid/alkali Acid/alkaliAcid/alkali Reducing agent Nil Nil {circle around (12)} Acid/alkaliAcid/alkali Acid/alkali Nil Nil Nil {circle around (13)} Acid/alkaliAcid/alkali Weak oxidizing Acid/alkali Nil Nil agent/cyan-based {circlearound (14)} Acid/alkali Acid/alkali Weak oxidizing Weak oxidizing NilNil agent/cyan-based agent/cyan-based {circle around (15)} Acid/alkaliAcid/alkali Weak oxidizing Reducing agent Nil Nil agent/cyan-based{circle around (16)} Acid/alkali Acid/alkali Weak oxidizing Nil Nil Nilagent/cyan-based {circle around (17)} Acid/alkali Acid/alkali Reducingagent Acid/alkali Nil Nil {circle around (18)} Acid/alkali Acid/alkaliReducing agent Weak oxidizing Nil Nil agent/cyan-based {circle around(19)} Acid/alkali Acid/alkali Reducing agent Reducing agent Nil Nil{circle around (20)} Acid/alkali Acid/alkali Reducing agent Nil Nil Nil

TABLE 2-4 First Second Third Fourth First Second microbicide microbicidemicrobicide microbicide neutralizing agent neutralizing agent {circlearound (1)} Acid/alkali Weak oxidizing Strong oxidizing Acid/alkaliReducing agent Reducing agent agent/cyan-based agent {circle around (2)}Acid/alkali Weak oxidizing Strong oxidizing Weak oxidizing Reducingagent Reducing agent agent/cyan-based agent agent/cyan-based {circlearound (3)} Acid/alkali Weak oxidizing Strong oxidizing Reducing agentReducing agent Reducing agent agent/cyan-based agent {circle around (4)}Acid/alkali Weak oxidizing Strong oxidizing Nil Reducing agent Reducingagent agent/cyan-based agent {circle around (5)} Acid/alkali Weakoxidizing Strong oxidizing Acid/alkali Nil Nil agent/cyan-based agent{circle around (6)} Acid/alkali Weak oxidizing Strong oxidizing Weakoxidizing Nil Nil agent/cyan-based agent agent/cyan-based {circle around(7)} Acid/alkali Weak oxidizing Strong oxidizing Reducing agent Nil Nilagent/cyan-based agent {circle around (8)} Acid/alkali Weak oxidizingStrong oxidizing Nil Nil Nil agent/cyan-based agent {circle around (9)}Acid/alkali Weak oxidizing Acid/alkali Acid/alkali Nil Nilagent/cyan-based {circle around (10)} Acid/alkali Weak oxidizingAcid/alkali Weak oxidizing Nil Nil agent/cyan-based agent/cyan-based{circle around (11)} Acid/alkali Weak oxidizing Acid/alkali Reducingagent Nil Nil agent/cyan-based {circle around (12)} Acid/alkali Weakoxidizing Acid/alkali Nil Nil Nil agent/cyan-based {circle around (13)}Acid/alkali Weak oxidizing Weak oxidizing Acid/alkali Nil Nilagent/cyan-based agent/cyan-based {circle around (14)} Acid/alkali Weakoxidizing Weak oxidizing Weak oxidizing Nil Nil agent/cyan-basedagent/cyan-based agent/cyan-based {circle around (15)} Acid/alkali Weakoxidizing Weak oxidizing Reducing agent Nil Nil agent/cyan-basedagent/cyan-based {circle around (16)} Acid/alkali Weak oxidizing Weakoxidizing Nil Nil Nil agent/cyan-based agent/cyan-based {circle around(17)} Acid/alkali Weak oxidizing Reducing agent Acid/alkali Nil Nilagent/cyan-based {circle around (18)} Acid/alkali Weak oxidizingReducing agent Weak oxidizing Nil Nil agent/cyan-based agent/cyan-based{circle around (19)} Acid/alkali Weak oxidizing Reducing agent Reducingagent Nil Nil agent/cyan-based {circle around (20)} Acid/alkali Weakoxidizing Reducing agent Nil Nil Nil agent/cyan-based

TABLE 2-5 First Second Third Fourth First Second microbicide microbicidemicrobicide microbicide neutralizing agent neutralizing agent {circlearound (1)} Acid/alkali Reducing agent Strong oxidizing Acid/alkaliReducing agent Reducing agent agent {circle around (2)} Acid/alkaliReducing agent Strong oxidizing Weak oxidizing Reducing agent Reducingagent agent agent/cyan-based {circle around (3)} Acid/alkali Reducingagent Strong oxidizing Reducing agent Reducing agent Reducing agentagent {circle around (4)} Acid/alkali Reducing agent Strong oxidizingNil Reducing agent Reducing agent agent {circle around (5)} Acid/alkaliReducing agent Strong oxidizing Acid/alkali Nil Nil agent {circle around(6)} Acid/alkali Reducing agent Strong oxidizing Weak oxidizing Nil Nilagent agent/cyan-based {circle around (7)} Acid/alkali Reducing agentStrong oxidizing Reducing agent Nil Nil agent {circle around (8)}Acid/alkali Reducing agent Strong oxidizing Nil Nil Nil agent {circlearound (9)} Acid/alkali Reducing agent Acid/alkali Acid/alkali Nil Nil{circle around (10)} Acid/alkali Reducing agent Acid/alkali Weakoxidizing Nil Nil agent/cyan-based {circle around (11)} Acid/alkaliReducing agent Acid/alkali Reducing agent Nil Nil {circle around (12)}Acid/alkali Reducing agent Acid/alkali Nil Nil Nil {circle around (13)}Acid/alkali Reducing agent Weak oxidizing Acid/alkali Nil Nilagent/cyan-based {circle around (14)} Acid/alkali Reducing agent Weakoxidizing Weak oxidizing Nil Nil agent/cyan-based agent/cyan-based{circle around (15)} Acid/alkali Reducing agent Weak oxidizing Reducingagent Nil Nil agent/cyan-based {circle around (16)} Acid/alkali Reducingagent Weak oxidizing Nil Nil Nil agent/cyan-based {circle around (17)}Acid/alkali Reducing agent Reducing agent Acid/alkali Nil Nil {circlearound (18)} Acid/alkali Reducing agent Reducing agent Weak oxidizingNil Nil agent/cyan-based {circle around (19)} Acid/alkali Reducing agentReducing agent Reducing agent Nil Nil {circle around (20)} Acid/alkaliReducing agent Reducing agent Nil Nil Nil

TABLE 2-6 First Second Third Fourth First Second microbicide microbicidemicrobicide microbicide neutralizing agent neutralizing agent {circlearound (1)} Weak oxidizing Strong oxidizing Strong oxidizing Acid/alkaliReducing agent Reducing agent agent/cyan-based agent agent {circlearound (2)} Weak oxidizing Strong oxidizing Strong oxidizing Weakoxidizing Reducing agent Reducing agent agent/cyan-based agent agentagent/cyan-based {circle around (3)} Weak oxidizing Strong oxidizingStrong oxidizing Reducing agent Reducing agent Reducing agentagent/cyan-based agent agent {circle around (4)} Weak oxidizing Strongoxidizing Strong oxidizing Nil Reducing agent Reducing agentagent/cyan-based agent agent {circle around (5)} Weak oxidizing Strongoxidizing Strong oxidizing Acid/alkali Nil Reducing agentagent/cyan-based agent agent {circle around (6)} Weak oxidizing Strongoxidizing Strong oxidizing Weak oxidizing Nil Reducing agentagent/cyan-based agent agent agent/cyan-based {circle around (7)} Weakoxidizing Strong oxidizing Strong oxidizing Reducing agent Nil Reducingagent agent/cyan-based agent agent {circle around (8)} Weak oxidizingStrong oxidizing Strong oxidizing Nil Nil Reducing agentagent/cyan-based agent agent {circle around (9)} Weak oxidizing Strongoxidizing Acid/alkali Acid/alkali Nil Nil agent/cyan-based agent {circlearound (10)} Weak oxidizing Strong oxidizing Acid/alkali Weak oxidizingNil Nil agent/cyan-based agent agent/cyan-based {circle around (11)}Weak oxidizing Strong oxidizing Acid/alkali Reducing agent Nil Nilagent/cyan-based agent {circle around (12)} Weak oxidizing Strongoxidizing Acid/alkali Nil Nil Nil agent/cyan-based agent {circle around(13)} Weak oxidizing Strong oxidizing Weak oxidizing Acid/alkali Nil Nilagent/cyan-based agent agent/cyan-based {circle around (14)} Weakoxidizing Strong oxidizing Weak oxidizing Weak oxidizing Nil Nilagent/cyan-based agent agent/cyan-based agent/cyan-based {circle around(15)} Weak oxidizing Strong oxidizing Weak oxidizing Reducing agent NilNil agent/cyan-based agent agent/cyan-based {circle around (16)} Weakoxidizing Strong oxidizing Weak oxidizing Nil Nil Nil agent/cyan-basedagent agent/cyan-based {circle around (17)} Weak oxidizing Strongoxidizing Reducing agent Acid/alkali Nil Nil agent/cyan-based agent{circle around (18)} Weak oxidizing Strong oxidizing Reducing agent Weakoxidizing Nil Nil agent/cyan-based agent agent/cyan-based {circle around(19)} Weak oxidizing Strong oxidizing Reducing agent Reducing agent NilNil agent/cyan-based agent {circle around (20)} Weak oxidizing Strongoxidizing Reducing agent Nil Nil Nil agent/cyan-based agent

TABLE 2-7 First Second Third Fourth First Second microbicide microbicidemicrobicide microbicide neutralizing agent neutralizing agent {circlearound (1)} Weak oxidizing Nil Strong oxidizing Acid/alkali Reducingagent Nil agent/cyan-based agent {circle around (2)} Weak oxidizing NilStrong oxidizing Weak oxidizing Reducing agent Nil agent/cyan-basedagent agent/cyan-based {circle around (3)} Weak oxidizing Nil Strongoxidizing Reducing agent Reducing agent Nil agent/cyan-based agent{circle around (4)} Weak oxidizing Nil Strong oxidizing Nil Reducingagent Nil agent/cyan-based agent {circle around (5)} Weak oxidizing NilStrong oxidizing Acid/alkali Nil Reducing agent agent/cyan-based agent{circle around (6)} Weak oxidizing Nil Strong oxidizing Weak oxidizingNil Reducing agent agent/cyan-based agent agent/cyan-based {circlearound (7)} Weak oxidizing Nil Strong oxidizing Reducing agent NilReducing agent agent/cyan-based agent {circle around (8)} Weak oxidizingNil Strong oxidizing Nil Nil Reducing agent agent/cyan-based agent{circle around (9)} Weak oxidizing Nil Acid/alkali Acid/alkali Nil Nilagent/cyan-based {circle around (10)} Weak oxidizing Nil Acid/alkaliWeak oxidizing Nil Nil agent/cyan-based agent/cyan-based {circle around(11)} Weak oxidizing Nil Acid/alkali Reducing agent Nil Nilagent/cyan-based {circle around (12)} Weak oxidizing Nil Acid/alkali NilNil Nil agent/cyan-based {circle around (13)} Weak oxidizing Nil Weakoxidizing Acid/alkali Nil Nil agent/cyan-based agent/cyan-based {circlearound (14)} Weak oxidizing Nil Weak oxidizing Weak oxidizing Nil Nilagent/cyan-based agent/cyan-based agent/cyan-based {circle around (15)}Weak oxidizing Nil Weak oxidizing Reducing agent Nil Nilagent/cyan-based agent/cyan-based {circle around (16)} Weak oxidizingNil Weak oxidizing Nil Nil Nil agent/cyan-based agent/cyan-based {circlearound (17)} Weak oxidizing Nil Reducing agent Acid/alkali Nil Nilagent/cyan-based {circle around (18)} Weak oxidizing Nil Reducing agentWeak oxidizing Nil Nil agent/cyan-based agent/cyan-based {circle around(19)} Weak oxidizing Nil Reducing agent Reducing agent Nil Nilagent/cyan-based {circle around (20)} Weak oxidizing Nil Reducing agentNil Nil Nil agent/cyan-based

TABLE 2-8 First Second Third Fourth First Second microbicide microbicidemicrobicide microbicide neutralizing agent neutralizing agent {circlearound (1)} Weak oxidizing Acid/alkali Strong oxidizing Acid/alkaliReducing agent Reducing agent agent/cyan-based agent {circle around (2)}Weak oxidizing Acid/alkali Strong oxidizing Weak oxidizing Reducingagent Reducing agent agent/cyan-based agent agent/cyan-based {circlearound (3)} Weak oxidizing Acid/alkali Strong oxidizing Reducing agentReducing agent Reducing agent agent/cyan-based agent {circle around (4)}Weak oxidizing Acid/alkali Strong oxidizing Nil Reducing agent Reducingagent agent/cyan-based agent {circle around (5)} Weak oxidizingAcid/alkali Strong oxidizing Acid/alkali Nil Reducing agentagent/cyan-based agent {circle around (6)} Weak oxidizing Acid/alkaliStrong oxidizing Weak oxidizing Nil Reducing agent agent/cyan-basedagent agent/cyan-based {circle around (7)} Weak oxidizing Acid/alkaliStrong oxidizing Reducing agent Nil Reducing agent agent/cyan-basedagent {circle around (8)} Weak oxidizing Acid/alkali Strong oxidizingNil Nil Reducing agent agent/cyan-based agent {circle around (9)} Weakoxidizing Acid/alkali Acid/alkali Acid/alkali Nil Nil agent/cyan-based{circle around (10)} Weak oxidizing Acid/alkali Acid/alkali Weakoxidizing Nil Nil agent/cyan-based agent/cyan-based {circle around (11)}Weak oxidizing Acid/alkali Acid/alkali Reducing agent Nil Nilagent/cyan-based {circle around (12)} Weak oxidizing Acid/alkaliAcid/alkali Nil Nil Nil agent/cyan-based {circle around (13)} Weakoxidizing Acid/alkali Weak oxidizing Acid/alkali Nil Nilagent/cyan-based agent/cyan-based {circle around (14)} Weak oxidizingAcid/alkali Weak oxidizing Weak oxidizing Nil Nil agent/cyan-basedagent/cyan-based agent/cyan-based {circle around (15)} Weak oxidizingAcid/alkali Weak oxidizing Reducing agent Nil Nil agent/cyan-basedagent/cyan-based {circle around (16)} Weak oxidizing Acid/alkali Weakoxidizing Nil Nil Nil agent/cyan-based agent/cyan-based {circle around(17)} Weak oxidizing Acid/alkali Reducing agent Acid/alkali Nil Nilagent/cyan-based {circle around (18)} Weak oxidizing Acid/alkaliReducing agent Weak oxidizing Nil Nil agent/cyan-based agent/cyan-based{circle around (19)} Weak oxidizing Acid/alkali Reducing agent Reducingagent Nil Nil agent/cyan-based {circle around (20)} Weak oxidizingAcid/alkali Reducing agent Nil Nil Nil agent/cyan-based

TABLE 2-9 First Second Third Fourth First Second microbicide microbicidemicrobicide microbicide neutralizing agent neutralizing agent {circlearound (1)} Weak oxidizing Weak oxidizing Strong oxidizing Acid/alkaliReducing agent Reducing agent agent/cyan-based agent/cyan-based agent{circle around (2)} Weak oxidizing Weak oxidizing Strong oxidizing Weakoxidizing Reducing agent Reducing agent agent/cyan-basedagent/cyan-based agent agent/cyan-based {circle around (3)} Weakoxidizing Weak oxidizing Strong oxidizing Reducing agent Reducing agentReducing agent agent/cyan-based agent/cyan-based agent {circle around(4)} Weak oxidizing Weak oxidizing Strong oxidizing Nil Reducing agentReducing agent agent/cyan-based agent/cyan-based agent {circle around(5)} Weak oxidizing Weak oxidizing Strong oxidizing Acid/alkali NilReducing agent agent/cyan-based agent/cyan-based agent {circle around(6)} Weak oxidizing Weak oxidizing Strong oxidizing Weak oxidizing NilReducing agent agent/cyan-based agent/cyan-based agent agent/cyan-based{circle around (7)} Weak oxidizing Weak oxidizing Strong oxidizingReducing agent Nil Reducing agent agent/cyan-based agent/cyan-basedagent {circle around (8)} Weak oxidizing Weak oxidizing Strong oxidizingNil Nil Reducing agent agent/cyan-based agent/cyan-based agent {circlearound (9)} Weak oxidizing Weak oxidizing Acid/alkali Acid/alkali NilNil agent/cyan-based agent/cyan-based {circle around (10)} Weakoxidizing Weak oxidizing Acid/alkali Weak oxidizing Nil Nilagent/cyan-based agent/cyan-based agent/cyan-based {circle around (11)}Weak oxidizing Weak oxidizing Acid/alkali Reducing agent Nil Nilagent/cyan-based agent/cyan-based {circle around (12)} Weak oxidizingWeak oxidizing Acid/alkali Nil Nil Nil agent/cyan-based agent/cyan-based{circle around (13)} Weak oxidizing Weak oxidizing Weak oxidizingAcid/alkali Nil Nil agent/cyan-based agent/cyan-based agent/cyan-based{circle around (14)} Weak oxidizing Weak oxidizing Weak oxidizing Weakoxidizing Nil Nil agent/cyan-based agent/cyan-based agent/cyan-basedagent/cyan-based {circle around (15)} Weak oxidizing Weak oxidizing Weakoxidizing Reducing agent Nil Nil agent/cyan-based agent/cyan-basedagent/cyan-based {circle around (16)} Weak oxidizing Weak oxidizing Weakoxidizing Nil Nil Nil agent/cyan-based agent/cyan-based agent/cyan-based{circle around (17)} Weak oxidizing Weak oxidizing Reducing agentAcid/alkali Nil Nil agent/cyan-based agent/cyan-based {circle around(18)} Weak oxidizing Weak oxidizing Reducing agent Weak oxidizing NilNil agent/cyan-based agent/cyan-based agent/cyan-based {circle around(19)} Weak oxidizing Weak oxidizing Reducing agent Reducing agent NilNil agent/cyan-based agent/cyan-based {circle around (20)} Weakoxidizing Weak oxidizing Reducing agent Nil Nil Nil agent/cyan-basedagent/cyan-based

TABLE 2-10 First Second Third Fourth First Second microbicidemicrobicide microbicide microbicide neutralizing agent neutralizingagent {circle around (1)} Weak oxidizing Reducing agent Strong oxidizingAcid/alkali Reducing agent Reducing agent agent/cyan-based agent {circlearound (2)} Weak oxidizing Reducing agent Strong oxidizing Weakoxidizing Reducing agent Reducing agent agent/cyan-based agentagent/cyan-based {circle around (3)} Weak oxidizing Reducing agentStrong oxidizing Reducing agent Reducing agent Reducing agentagent/cyan-based agent {circle around (4)} Weak oxidizing Reducing agentStrong oxidizing Nil Reducing agent Reducing agent agent/cyan-basedagent {circle around (5)} Weak oxidizing Reducing agent Strong oxidizingAcid/alkali Nil Reducing agent agent/cyan-based agent {circle around(6)} Weak oxidizing Reducing agent Strong oxidizing Weak oxidizing NilReducing agent agent/cyan-based agent agent/cyan-based {circle around(7)} Weak oxidizing Reducing agent Strong oxidizing Reducing agent NilReducing agent agent/cyan-based agent {circle around (8)} Weak oxidizingReducing agent Strong oxidizing Nil Nil Reducing agent agent/cyan-basedagent {circle around (9)} Weak oxidizing Reducing agent Acid/alkaliAcid/alkali Nil Nil agent/cyan-based {circle around (10)} Weak oxidizingReducing agent Acid/alkali Weak oxidizing Nil Nil agent/cyan-basedagent/cyan-based {circle around (11)} Weak oxidizing Reducing agentAcid/alkali Reducing agent Nil Nil agent/cyan-based {circle around (12)}Weak oxidizing Reducing agent Acid/alkali Nil Nil Nil agent/cyan-based{circle around (13)} Weak oxidizing Reducing agent Weak oxidizingAcid/alkali Nil Nil agent/cyan-based agent/cyan-based {circle around(14)} Weak oxidizing Reducing agent Weak oxidizing Weak oxidizing NilNil agent/cyan-based agent/cyan-based agent/cyan-based {circle around(15)} Weak oxidizing Reducing agent Weak oxidizing Reducing agent NilNil agent/cyan-based agent/cyan-based {circle around (16)} Weakoxidizing Reducing agent Weak oxidizing Nil Nil Nil agent/cyan-basedagent/cyan-based {circle around (17)} Weak oxidizing Reducing agentReducing agent Acid/alkali Nil Nil agent/cyan-based {circle around (18)}Weak oxidizing Reducing agent Reducing agent Weak oxidizing Nil Nilagent/cyan-based agent/cyan-based {circle around (19)} Weak oxidizingReducing agent Reducing agent Reducing agent Nil Nil agent/cyan-based{circle around (20)} Weak oxidizing Reducing agent Reducing agent NilNil Nil agent/cyan-based

TABLE 2-11 First Second Third Fourth First Second microbicidemicrobicide microbicide microbicide neutralizing agent neutralizingagent {circle around (1)} Reducing agent Strong oxidizing Strongoxidizing Acid/alkali Reducing agent Reducing agent agent agent {circlearound (2)} Reducing agent Strong oxidizing Strong oxidizing Weakoxidizing Reducing agent Reducing agent agent agent agent/cyan-based{circle around (3)} Reducing agent Strong oxidizing Strong oxidizingReducing agent Reducing agent Reducing agent agent agent {circle around(4)} Reducing agent Strong oxidizing Strong oxidizing Nil Reducing agentReducing agent agent agent {circle around (5)} Reducing agent Strongoxidizing Strong oxidizing Acid/alkali Nil Reducing agent agent agent{circle around (6)} Reducing agent Strong oxidizing Strong oxidizingWeak oxidizing Nil Reducing agent agent agent agent/cyan-based {circlearound (7)} Reducing agent Strong oxidizing Strong oxidizing Reducingagent Nil Reducing agent agent agent {circle around (8)} Reducing agentStrong oxidizing Strong oxidizing Nil Nil Reducing agent agent agent{circle around (9)} Reducing agent Strong oxidizing Acid/alkaliAcid/alkali Nil Nil agent {circle around (10)} Reducing agent Strongoxidizing Acid/alkali Weak oxidizing Nil Nil agent agent/cyan-based{circle around (11)} Reducing agent Strong oxidizing Acid/alkaliReducing agent Nil Nil agent {circle around (12)} Reducing agent Strongoxidizing Acid/alkali Nil Nil Nil agent {circle around (13)} Reducingagent Strong oxidizing Weak oxidizing Acid/alkali Nil Nil agentagent/cyan-based {circle around (14)} Reducing agent Strong oxidizingWeak oxidizing Weak oxidizing Nil Nil agent agent/cyan-basedagent/cyan-based {circle around (15)} Reducing agent Strong oxidizingWeak oxidizing Reducing agent Nil Nil agent agent/cyan-based {circlearound (16)} Reducing agent Strong oxidizing Weak oxidizing Nil Nil Nilagent agent/cyan-based {circle around (17)} Reducing agent Strongoxidizing Reducing agent Acid/alkali Nil Nil agent {circle around (18)}Reducing agent Strong oxidizing Reducing agent Weak oxidizing Nil Nilagent agent/cyan-based {circle around (19)} Reducing agent Strongoxidizing Reducing agent Reducing agent Nil Nil agent {circle around(20)} Reducing agent Strong oxidizing Reducing agent Nil Nil Nil agent

TABLE 2-12 First Second Third Fourth First Second microbicidemicrobicide microbicide microbicide neutralizing agent neutralizingagent {circle around (1)} Reducing agent Nil Strong oxidizingAcid/alkali Reducing agent Nil agent {circle around (2)} Reducing agentNil Strong oxidizing Weak oxidizing Reducing agent Nil agentagent/cyan-based {circle around (3)} Reducing agent Nil Strong oxidizingReducing agent Reducing agent Nil agent {circle around (4)} Reducingagent Nil Strong oxidizing Nil Reducing agent Nil agent {circle around(5)} Reducing agent Nil Strong oxidizing Acid/alkali Nil Reducing agentagent {circle around (6)} Reducing agent Nil Strong oxidizing Weakoxidizing Nil Reducing agent agent agent/cyan-based {circle around (7)}Reducing agent Nil Strong oxidizing Reducing agent Nil Reducing agentagent {circle around (8)} Reducing agent Nil Strong oxidizing Nil NilReducing agent agent {circle around (9)} Reducing agent Nil Acid/alkaliAcid/alkali Nil Nil {circle around (10)} Reducing agent Nil Acid/alkaliWeak oxidizing Nil Nil agent/cyan-based {circle around (11)} Reducingagent Nil Acid/alkali Reducing agent Nil Nil {circle around (12)}Reducing agent Nil Acid/alkali Nil Nil Nil {circle around (13)} Reducingagent Nil Weak oxidizing Acid/alkali Nil Nil agent/cyan-based {circlearound (14)} Reducing agent Nil Weak oxidizing Weak oxidizing Nil Nilagent/cyan-based agent/cyan-based {circle around (15)} Reducing agentNil Weak oxidizing Reducing agent Nil Nil agent/cyan-based {circlearound (16)} Reducing agent Nil Weak oxidizing Nil Nil Nilagent/cyan-based {circle around (17)} Reducing agent Nil Reducing agentAcid/alkali Nil Nil {circle around (18)} Reducing agent Nil Reducingagent Weak oxidizing Nil Nil agent/cyan-based {circle around (19)}Reducing agent Nil Reducing agent Reducing agent Nil Nil {circle around(20)} Reducing agent Nil Reducing agent Nil Nil Nil

TABLE 2-13 First Second Third Fourth First Second microbicidemicrobicide microbicide microbicide neutralizing agent neutralizingagent {circle around (1)} Reducing agent Acid/alkali Strong oxidizingAcid/alkali Reducing agent Reducing agent agent {circle around (2)}Reducing agent Acid/alkali Strong oxidizing Weak oxidizing Reducingagent Reducing agent agent agent/cyan-based {circle around (3)} Reducingagent Acid/alkali Strong oxidizing Reducing agent Reducing agentReducing agent agent {circle around (4)} Reducing agent Acid/alkaliStrong oxidizing Nil Reducing agent Reducing agent agent {circle around(5)} Reducing agent Acid/alkali Strong oxidizing Acid/alkali NilReducing agent agent {circle around (6)} Reducing agent Acid/alkaliStrong oxidizing Weak oxidizing Nil Reducing agent agentagent/cyan-based {circle around (7)} Reducing agent Acid/alkali Strongoxidizing Reducing agent Nil Reducing agent agent {circle around (8)}Reducing agent Acid/alkali Strong oxidizing Nil Nil Reducing agent agent{circle around (9)} Reducing agent Acid/alkali Acid/alkali Acid/alkaliNil Nil {circle around (10)} Reducing agent Acid/alkali Acid/alkali Weakoxidizing Nil Nil agent/cyan-based {circle around (11)} Reducing agentAcid/alkali Acid/alkali Reducing agent Nil Nil {circle around (12)}Reducing agent Acid/alkali Acid/alkali Nil Nil Nil {circle around (13)}Reducing agent Acid/alkali Weak oxidizing Acid/alkali Nil Nilagent/cyan-based {circle around (14)} Reducing agent Acid/alkali Weakoxidizing Weak oxidizing Nil Nil agent/cyan-based agent/cyan-based{circle around (15)} Reducing agent Acid/alkali Weak oxidizing Reducingagent Nil Nil agent/cyan-based {circle around (16)} Reducing agentAcid/alkali Weak oxidizing Nil Nil Nil agent/cyan-based {circle around(17)} Reducing agent Acid/alkali Reducing agent Acid/alkali Nil Nil{circle around (18)} Reducing agent Acid/alkali Reducing agent Weakoxidizing Nil Nil agent/cyan-based {circle around (19)} Reducing agentAcid/alkali Reducing agent Reducing agent Nil Nil {circle around (20)}Reducing agent Acid/alkali Reducing agent Nil Nil Nil

TABLE 2-14 First Second Third Fourth First Second microbicidemicrobicide microbicide microbicide neutralizing agent neutralizingagent {circle around (1)} Reducing agent Weak oxidizing Strong oxidizingAcid/alkali Reducing agent Reducing agent agent/cyan-based agent {circlearound (2)} Reducing agent Weak oxidizing Strong oxidizing Weakoxidizing Reducing agent Reducing agent agent/cyan-based agentagent/cyan-based {circle around (3)} Reducing agent Weak oxidizingStrong oxidizing Reducing agent Reducing agent Reducing agentagent/cyan-based agent {circle around (4)} Reducing agent Weak oxidizingStrong oxidizing Nil Reducing agent Reducing agent agent/cyan-basedagent {circle around (5)} Reducing agent Weak oxidizing Strong oxidizingAcid/alkali Nil Reducing agent agent/cyan-based agent {circle around(6)} Reducing agent Weak oxidizing Strong oxidizing Weak oxidizing NilReducing agent agent/cyan-based agent agent/cyan-based {circle around(7)} Reducing agent Weak oxidizing Strong oxidizing Reducing agent NilReducing agent agent/cyan-based agent {circle around (8)} Reducing agentWeak oxidizing Strong oxidizing Nil Nil Reducing agent agent/cyan-basedagent {circle around (9)} Reducing agent Weak oxidizing Acid/alkaliAcid/alkali Nil Nil agent/cyan-based {circle around (10)} Reducing agentWeak oxidizing Acid/alkali Weak oxidizing Nil Nil agent/cyan-basedagent/cyan-based {circle around (11)} Reducing agent Weak oxidizingAcid/alkali Reducing agent Nil Nil agent/cyan-based {circle around (12)}Reducing agent Weak oxidizing Acid/alkali Nil Nil Nil agent/cyan-based{circle around (13)} Reducing agent Weak oxidizing Weak oxidizingAcid/alkali Nil Nil agent/cyan-based agent/cyan-based {circle around(14)} Reducing agent Weak oxidizing Weak oxidizing Weak oxidizing NilNil agent/cyan-based agent/cyan-based agent/cyan-based {circle around(15)} Reducing agent Weak oxidizing Weak oxidizing Reducing agent NilNil agent/cyan-based agent/cyan-based {circle around (16)} Reducingagent Weak oxidizing Weak oxidizing Nil Nil Nil agent/cyan-basedagent/cyan-based {circle around (17)} Reducing agent Weak oxidizingReducing agent Acid/alkali Nil Nil agent/cyan-based {circle around (18)}Reducing agent Weak oxidizing Reducing agent Weak oxidizing Nil Nilagent/cyan-based agent/cyan-based {circle around (19)} Reducing agentWeak oxidizing Reducing agent Reducing agent Nil Nil agent/cyan-based{circle around (20)} Reducing agent Weak oxidizing Reducing agent NilNil Nil agent/cyan-based

TABLE 2-15 First Second Third Fourth First Second microbicidemicrobicide microbicide microbicide neutralizing agent neutralizingagent {circle around (1)} Reducing agent Reducing agent Strong oxidizingAcid/alkali Reducing agent Reducing agent agent {circle around (2)}Reducing agent Reducing agent Strong oxidizing Weak oxidizing Reducingagent Reducing agent agent agent/cyan-based {circle around (3)} Reducingagent Reducing agent Strong oxidizing Reducing agent Reducing agentReducing agent agent {circle around (4)} Reducing agent Reducing agentStrong oxidizing Nil Reducing agent Reducing agent agent {circle around(5)} Reducing agent Reducing agent Strong oxidizing Acid/alkali NilReducing agent agent {circle around (6)} Reducing agent Reducing agentStrong oxidizing Weak oxidizing Nil Reducing agent agentagent/cyan-based {circle around (7)} Reducing agent Reducing agentStrong oxidizing Reducing agent Nil Reducing agent agent {circle around(8)} Reducing agent Reducing agent Strong oxidizing Nil Nil Reducingagent agent {circle around (9)} Reducing agent Reducing agentAcid/alkali Acid/alkali Nil Nil {circle around (10)} Reducing agentReducing agent Acid/alkali Weak oxidizing Nil Nil agent/cyan-based{circle around (11)} Reducing agent Reducing agent Acid/alkali Reducingagent Nil Nil {circle around (12)} Reducing agent Reducing agentAcid/alkali Nil Nil Nil {circle around (13)} Reducing agent Reducingagent Weak oxidizing Acid/alkali Nil Nil agent/cyan-based {circle around(14)} Reducing agent Reducing agent Weak oxidizing Weak oxidizing NilNil agent/cyan-based agent/cyan-based {circle around (15)} Reducingagent Reducing agent Weak oxidizing Reducing agent Nil Nilagent/cyan-based {circle around (16)} Reducing agent Reducing agent Weakoxidizing Nil Nil Nil agent/cyan-based {circle around (17)} Reducingagent Reducing agent Reducing agent Acid/alkali Nil Nil {circle around(18)} Reducing agent Reducing agent Reducing agent Weak oxidizing NilNil agent/cyan-based {circle around (19)} Reducing agent Reducing agentReducing agent Reducing agent Nil Nil {circle around (20)} Reducingagent Reducing agent Reducing agent Nil Nil Nil

Further, in the case where the water (A) undergoing treatment or thewater (B) undergoing treatment contains a strong oxidizing agent such asfree chlorine to such an extent that the semipermeable membrane isdeteriorated, it is preferred to reduce free chlorine by controlling theORP value using a reducing agent in order not to deteriorate thesemipermeable membrane treatment apparatus (A)(2) or the semipermeablemembrane treatment apparatus (B)(6). However, in this case, in orderthat the measured value by the ORP meter is not adversely affected by aninjected acid or alkali, it is preferred to use a system as shown inFIG. 2. In the case where a first chemical tank (10) or second chemicaltank (20) or third chemical tank (30) or fourth chemical tank (40)contains an acid or alkali, it is preferred to reduce free chlorine onthe side upstream of the place where the acid or alkali is injected inorder to reliably reduce and remove the free chlorine from the watersupplied to the semipermeable membrane. In the case where an acid oralkali is injected at a position upstream of the water mixing tank (5),it is preferred to reduce and remove the free chlorine from both thewater (A) undergoing treatment and the water (B) undergoing treatment.Further, in the case where an acid or alkali is injected at a positiondownstream of the water mixing tank (5), it is preferred to remove freechlorine from the mixed water since only one chemical tank is necessary.Consequently in FIG. 2, in the case where the first chemical is an acidor alkali, in the semipermeable membrane treatment process (A)(100), afifth chemical in a fifth chemical tank (50) is injected into the water(A) undergoing treatment by a fifth chemical feed pump (51), and furtherin the semipermeable membrane treatment process (B), a fifth chemical ina fifth chemical tank (60) is injected into the water (B) undergoingtreatment by a fifth chemical feed pump (61).

As the method for adjusting the injection amount of the fifth chemical,a method in which an ORP meter is installed in the tank used forinjecting the fifth chemical, to adjust the injection amount in orderthat the water in the tank may have a specified ORP value, or a methodin which an ORP meter, a chemical injection point and another ORP meterare disposed in this order from the upstream side, to ensure that whenthe ORP meter on the side upstream of the chemical injection pointindicates a value larger than a specified value, the injection of thechemical can be started and that when the ORP meter on the sidedownstream of the chemical injection point indicates a value within aspecified range of values, the injection of the chemical is stopped, arepreferred for such reasons that the free chlorine can be reliablyreduced and that the free chlorine does not flow into the semipermeablemembrane, hence does not deteriorate the semipermeable membrane. In FIG.2, a first ORP meter (116) is installed at a position upstream of theinjection point of the fifth chemical feed pump (51), and a second ORPmeter (117) is installed at a position downstream of the injectionpoint. Further, a first ORP meter (118) is installed at a positionupstream of the injection point of the fifth chemical feed pump (61) anda second ORP meter (119) is installed at a position downstream of theinjection point. In reference to the ORP values of the respective ORPmeters, the injection of the fifth chemical is started and stopped.Meanwhile, it is preferred that a line mixer is installed between eachfifth chemical feed pump and the ORP meter downstream of it, since theliquid and the fifth chemical can be reliably mixed.

Further, since the concentrated water (A) is the water obtained byconcentrating the water (A) undergoing treatment, the ORP value maybecome larger than a specified value, depending on the change of thewater quality of the water (A) undergoing treatment. In this case, ifthe concentrated water (A) is mixed with the water (B) undergoingtreatment, it is highly possible that the semipermeable membrane (B) isdeteriorated. Therefore, it is preferred to discharge the concentratedwater (A) outside the system without using it as the water supplied tothe semipermeable membranes (B). For this reason, in FIG. 3 (a flowchartshowing an embodiment of the fresh water production system to which theinvention is applied), a third ORP meter (120) for measuring the ORPvalue of the concentrated water (A) is installed in the concentratedwater (A) feed piping (104). In the case where the ORP value of thethird ORP meter (120) becomes larger than a specified value, a three-wayvalve (121) is switched so that the concentrated water (A) may beswitched from the water mixing tank to the drain pipe side, for beingdischarged outside the system. Further, lest the semipermeable membranetreatment apparatus (B)(6) should be damaged by change in the amount ofthe mixed water or in the osmotic pressure of the mixed water, a boosterpump (112) is stopped to stop the semipermeable membrane treatment.

Further, it is preferred that the aforementioned semipermeable membranetreatment apparatus (A) is provided with chlorine-resistantsemipermeable membranes, and that the first chemical is achlorine-resistant chemical. If this mode is employed, a chlorine-basedchemical such as sodium hypochlorite usually used forwashing/sterilizing pipings can be used as the first chemical, and stillafter washing/sterilizing the semipermeable membrane treatment apparatus(A), it can be used as it is for washing/sterilizing the concentratedwater piping of the semipermeable membrane treatment apparatus (A) andthe semipermeable membrane treatment apparatus (B).

Further, it is preferred that the semipermeable membrane treatment(B)(6) is provided with chlorine-resistant semipermeable membranes, andthat at least one chemical selected from the second, third and fourthchemicals are a chlorine-resistant chemical. If this mode is employed,the chlorine-resistant chemical having been used for washing the pipingcan be used as it is for washing/sterilizing the semipermeable membranetreatment apparatus (B)(6).

In the above, a chlorine-resistant semipermeable membrane refers to asemipermeable membrane that satisfies B/A≧0.9, where A denotes thesodium chloride blocking rate after the semipermeable membrane isoperated in an aqueous solution containing 1,500 ppm of sodium chlorideadjusted to pH 6.5 at 25° C. and at an operation pressure of 5 kg/cm²for 30 minutes, and B denotes the sodium chloride blocking rate afterthe same semipermeable membrane is immersed in the abovementioned sodiumchloride aqueous solution further containing 100 ppm of sodiumhypochlorite and adjusted by potassium dihydrogenphosphate to pH 6.5 for48 hours and subsequently operated at an operation pressure of 5 kg/cm²for 30 minutes. The material of the membrane can be, for example, acellulose triacetate membrane or a chlorine-resistant polyamidemembrane.

Further, in the case where a chlorine-resistant chemical is used as thesecond chemical to be injected into the water (B) undergoing treatment,if nitrogen-containing water is supplied as the water (A) undergoingtreatment or if a nitrogen-containing chemical is injected into thewater (A) undergoing treatment or the concentrated water (A) or themixed water, chlorine and ammonia nitrogen react with each other in thewater mixing tank (5), to generate chloramines, and consequently thechloramines can be used to wash the semipermeable membrane treatmentapparatus (B)(6). Especially in the case where the semipermeablemembrane treatment apparatus (B)(6) uses polyamide-based semipermeablemembranes and is deteriorated by chlorine-containing water, it ispreferred to use the chloramines for inhibiting biofouling. In thiscase, nitrogen-containing water refers to the water obtained bybiologically treating livestock wastewater, human waste, sewage or thelike containing nitrogen-containing materials in water by an activatedsludge method. The nitrogen-containing materials contained in thenitrogen-containing water refer to nitrogen-containing organic compoundssuch as ammonia nitrogen, amino acids and amines. The nitrogen-basedcomponents in the nitrogen-containing organic compounds react withchlorine, to produce chloramines.

For example, in the case where most of the nitrogen-based componentscontained in nitrogen-containing water are ammonia nitrogen, it reactswith chlorine according to the following reaction, to producemonochloramine.

NH₃+Cl₂

NH₂Cl+HCl  [Chemical formula 1]

In this case, approx. 5 g of chlorine is consumed per 1 g of ammonianitrogen, to produce approx. 3.6 g of monochloramine. In order to keepthe chloramine content at an adequate level, it is preferred that theammonia nitrogen concentration in the nitrogen-containing water is 0.003mg/l or more. Further, it is preferred that the free chlorineconcentration in the concentrated water (A) made to flow into the watermixing tank (13) is 7 mg/l or less.

To measure the chloramine concentration and the free chlorineconcentration, a DPD method, current method, absorptiometry, etc. areused. The chloramine concentration can be obtained by obtaining a totalchlorine concentration consisting of the chloramine concentration andthe free chlorine concentration and subtracting the free chlorineconcentration from the total chlorine concentration. For example, themixed water flowing into the semipermeable membrane treatment apparatus(B)(6) is sampled, and the total chlorine concentration and the freechlorine concentration are measured under ordinary measuring conditionsby a DPD method or current method. Otherwise, a continuous automaticmeasuring instrument using absorptiometry can be used to measure thetotal chlorine concentration and the free chlorine concentration. In thecase where a continuous automatic measuring instrument is used formeasurement, a chlorine concentration meter is attached to the mixedwater feed piping (105), to perform continuous measurement for measuringthe chloramine concentration in the mixed water flowing into thesemipermeable membrane treatment apparatus (B)(6). By this measurement,the chloramine concentration and the free chlorine concentration aremonitored to take actions for keeping the concentrations withinpredetermined ranges.

Further, the chlorine in water exists as free chlorine and boundchlorine. The chlorine contained in the chlorine-containing water isfree chlorine, and if it reacts with a nitrogen-containing material,bound chlorine is formed. Bound chlorine refers to the chlorine existingas a chloramine(s).

A chloramine is a general term for monochloramine (NH₂Cl), dichloramine(NHCl₂) and trichloramine (NCl₃). Dichloramine is larger thanmonochloramine in microbicidal power, and trichloramine does not havemicrobicidal power. The production ratio of the chloramines changes,being affected by the chlorine concentration, amine compoundconcentration, pH, etc. Further, the microbicidal power of chloraminesis approximately one tenth of that of free chlorine, and far lessadversely affects the semipermeable membranes than free chlorine.

Free chlorine refers to the chlorine that exists as hypochlorous acid(HClO) and hypochlorite ions (ClO⁻) produced when chlorine compoundsreact with water, and has high disinfection power and oxidizing power.Free chlorine has strong oxidizing power. Consequently if the waterflowing into semipermeable membranes contains free chlorine, thesemipermeable membranes will be deteriorated. Therefore, if the waterflowing into RO membranes or NF membranes contains free chlorine, thereoccurs a problem that the membranes are deteriorated to aggravate thequality of the treated water.

Further, in order to allow the chloramines in mixed water tosufficiently exhibit a membrane sterilization effect in thesemipermeable membrane treatment apparatus (B)(6), for thereby allowingbiofouling to be inhibited and for preventing the functional layers ofthe semipermeable membranes from being deteriorated, it is preferredthat the chloramine concentration in the mixed water supplied to thesemipermeable membrane treatment apparatus (B)(6) is kept in a rangefrom 0.01 to 5 mg/l. If the chloramine concentration is lower than 0.01mg/l, biofouling cannot be inhibited. If the chloramine concentration ishigher than 5 mg/l, the functional layers of the membranes aredeteriorated.

This invention provides a fresh water production method using acomposite water treatment technology with multiple semipermeablemembrane units disposed, and can be suitably applied in the case wherewater (A) undergoing treatment and water (B) undergoing treatmentdifferent in osmotic pressure such as sewage and seawater as multipletypes of raw water are used to produce fresh water by a desalinationtechnology. In more detail, this invention can be applied as a freshwater production equipment in the water purification field for publicwater supply and in the industrial fresh water production field forproducing industrial water, food and medical process water andsemiconductor related washing water, and allows energy-saving efficientproduction of fresh water.

MEANINGS OF SYMBOLS

-   1: water (A) undergoing treatment-   2: semipermeable membrane treatment apparatus (A)-   3: membrane-permeating water (A)-   4: water (B) undergoing treatment-   5: water mixing tank-   6: semipermeable membrane treatment apparatus (B)-   7: membrane-permeating water (B)-   8: concentrated water (B)-   10: first chemical tank-   11: first chemical feed pump-   20: second chemical tank-   21: second chemical feed pump-   30: third chemical tank-   31: third chemical feed pump-   40: fourth chemical tank-   41: fourth chemical feed pump-   50: fifth chemical tank-   51: fifth chemical feed pump-   60: fifth chemical tank-   61: fifth chemical feed pump-   70: first neutralizing agent tank-   71: first neutralizing agent feed pump-   80: second neutralizing agent tank-   81: second neutralizing agent feed pump-   100: semipermeable membrane treatment process (A)-   101: water (A) undergoing treatment feed piping-   102: membrane-permeating water piping-   103: water (B) undergoing treatment feed piping-   104: concentrated water (A) feed piping-   105: mixed water feed piping-   106: membrane-permeating water piping-   107: concentrated water piping-   111: booster pump-   112: booster pump-   113: safety filter-   114: first meter-   115: second meter-   116: first ORP meter-   117: second ORP meter-   118: first ORP meter-   119: second ORP meter-   120: third ORP meter-   121: three-way valve-   200: semipermeable membrane treatment process (B)

1. A fresh water production method comprising treating water (A)undergoing treatment by a semipermeable membrane treatment apparatus(A), to produce fresh water, mixing the concentrated water (A) producedby the treatment in the semipermeable membrane treatment apparatus (A)with water (B) undergoing treatment, and treating the mixed water by asemipermeable membrane treatment apparatus (B), to produce fresh water,wherein a first chemical is continuously or intermittently injected intothe water (A) undergoing treatment and a second chemical is continuouslyor intermittently injected into the water (B) undergoing treatment.
 2. Afresh water production method, according to claim 1, wherein a thirdchemical is continuously or intermittently injected into theconcentrated water (A) and/or a fourth chemical is continuously orintermittently injected into the mixed water.
 3. A fresh waterproduction method, according to claim 1, wherein the concentration ofthe first chemical in the concentrated water (A) as discharged from thesemipermeable membrane treatment apparatus (A) is larger than theconcentration of the first chemical in the water (A) undergoingtreatment as supplied to the semipermeable membrane treatment apparatus(A).
 4. A fresh water production method, according to claim 1, wherein afirst neutralizing agent with an effect of eliminating or decreasing thewashing effect and sterilization effect of the second chemical iscontinuously or intermittently injected at a position between a meansfor injecting the second chemical and a water mixing means for mixingthe concentrated water (A) and the water (B) undergoing treatment.
 5. Afresh water production method, according to claim 4, wherein the firstneutralizing agent has an effect of eliminating or decreasing thewashing effect and sterilization effect of at least one chemicalselected from the first, third and fourth chemicals.
 6. A fresh waterproduction method, according to claim 5, wherein the first neutralizingagent is intermittently injected and the first chemical is injectedwhile the injection of the first neutralizing agent is suspended, and/orthe third chemical is injected while the injection of the firstneutralizing agent is suspended, and/or the fourth chemical is injectedwhile the injection of the first neutralizing agent is suspended.
 7. Afresh water production method, according to claim 2, wherein a secondneutralizing agent with an effect of eliminating or decreasing thewashing effect and sterilization effect of at least one chemicalselected from the first, second and third chemicals is injectedcontinuously or intermittently at a position between the water mixingmeans for mixing the concentrated water (A) and the water (B) undergoingtreatment and a means for injecting the fourth chemical.
 8. A freshwater production method, according to claim 7, wherein the secondneutralizing agent and the fourth chemical are intermittently injected,and the fourth chemical is injected while the injection of the secondneutralizing agent is suspended.
 9. A fresh water production method,according to claim 1, wherein in the case where the first chemical is ofthe type identical to that of at least one chemical selected from thesecond, third and fourth chemicals, the chemical of the identical typeis injected in such a manner that at least a portion of the chemical ofthe identical type can be mixed with the first chemical.
 10. A freshwater production method, according to claim 2, wherein in the case wherethe fourth chemical is of a type identical to that of at least onechemical selected from the first, second and third chemicals, thechemical of the identical type is injected in such a manner that atleast a portion of the chemical of the identical type can be mixed withthe fourth chemical.
 11. A fresh water production method, according toclaim 1, wherein in the case where the first chemical is of a typedifferent from that of at least one chemical selected from the second,third and fourth chemicals, the chemical of the different type isinjected in such a manner that the chemical of the different type cannotbe mixed with the first chemical.
 12. A fresh water production method,according to claim 2, wherein in the case where the fourth chemical isof a type different from that at least one chemical selected from thefirst, second and third chemicals, the chemical of the different type isinjected in such a manner that the chemical of the different type cannotbe mixed with the fourth chemical.
 13. A fresh water production method,according to claim 10, wherein a first meter selected from the groupconsisting of a pH meter, ORP meter, chlorine concentration meter, ECmeter, TOC meter, ammonia meter, TN meter and DO meter is installedbetween the water mixing means for mixing the concentrated water (A) andthe aforementioned water (B) undergoing treatment and the fourthchemical injection means, wherein the injection amount of the fourthchemical is determined on the basis of the indicated value of the firstmeter.
 14. A fresh water production method, according to claim 1,wherein in the case where at least one chemical selected from the first,second, third and fourth chemicals is an acid or alkali, the ORP valueof the liquid is adjusted to be kept within a specified range of valuesat a position upstream of the injection point of the chemical.
 15. Afresh water production method, according to claim 14, wherein in thecase where at least one chemical selected from the first, second, thirdand fourth chemicals is an acid or alkali, a first ORP meter formeasuring the ORP value of the liquid, a fifth chemical injection meansfor continuously or intermittently injecting an oxidizing agent orreducing agent as a fifth chemical to the liquid, and a second ORP meterfor measuring the ORP value of the liquid containing the fifth chemicalinjected therein are installed in this order from the upstream side atpositions upstream of all the injection means of the acid and alkalichemicals; the start of injecting the oxidizing agent or reducing agentby the fifth chemical injection means is determined in reference to themeasured value of the first ORP meter; and the stop of the injection isdetermined in reference to the measured value of the second ORP meter.16. A fresh water production method, according to claim 1, wherein theORP value of the concentrated water (A) is measured, and if the ORPvalue is larger than a specified value, the concentrated water (A) isdischarged outside the equipment, and the semipermeable membranetreatment of the semipermeable membrane treatment apparatus (B) isstopped.
 17. A fresh water production method, according to claim 1,wherein the semipermeable membrane treatment apparatus (A) is providedwith chlorine-resistant semipermeable membranes and the first chemicalis a chlorine-based chemical.
 18. A fresh water production method,according to claim 1, wherein the semipermeable membrane treatmentapparatus (B) is provided with chlorine-resistant semipermeablemembranes and at least one chemical selected from the second, third andfourth chemicals is a chlorine-based chemical.
 19. A fresh waterproduction method, according to claim 1, wherein the second chemical isa chlorine-based chemical, and nitrogen-containing water is supplied asthe aforementioned water (A) undergoing treatment, and/or anitrogen-containing chemical is injected into the water (A) undergoingtreatment or the concentrated water (A) or the mixed water.